 Nonstandard Analysis and the Hyperreals  Jordi Gutierrez Hermoso; Math Forum, Ask Dr. Math FAQ
An essay introducing the most basic ideas of nonstandard analysis and the hyperreal number system. Contents: A Very Brief History of AlmostNothing and MorethanEverything; The Hyperreal WishList; Construction of the hyperreal numbers; Hyperreal arithmetic;
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 The Normal Curve and Galton's Board  Paul Trow
Describes a mechanical device, invented by the nineteenthcentury mathematician Francis Galton, that illustrates the Central Limit Theorem, by showing how a binomial distribution approximates a normal distribution.
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 The Normal Distribution  Balasubramanian Narasimhan
Normal distributions are a very important class of statistical distributions. All normal distributions are symmetric and have bellshaped density curves with a single peak. Different values of mu and theta yield different normal density curves and hence
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 Northeast Regional Climate Center (NRCC)  Department of Soil, Crop and Atmospheric Sciences, Cornell University
The NRCC serves a 12state region that includes Connecticut, Delaware, Massachusetts, Maryland, Maine, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and West Virginia, working to acquire and disseminate accurate, uptodate
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 Northern Ireland Statistics and Research Agency (NISRA)
The department of the United Kingdom government that collects statistics about Northern Ireland. Includes tables and graphs of key socioeconomic statistics, which are available for download as Lotus 123 worksheets; demographic data, available in Lotus
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 Northwest Math Conference
An annual conference that "brings together mathematics teachers from all levels of primary, secondary, and undergraduate education to learn and share about mathematics and pedagogy." Find information on Northwest Math Conference (NWMC) programs, speakers,
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 The Norwegian Mathematical Olympiad
Problems and solutions from the Abel Competition, the Norwegian Mathematical Competition (NMC), and the Baltic Way, dating back to 1992, many in English. The Norwegian Mathematical Olympiad is organized by the Norwegian Mathematical Society in cooperation
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 Norwegian Mathematical Society
Site is in Norwegian. Purpose, activities, history, membership, meetings.
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 Notation for some Knots (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
It is hard mathematically to completely codify all possible knots. Given two knots, it is difficult to tell whether they are the same. It is harder still to tell for sure that they are different. Many simple knots can be arranged in a form described
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 Not Dumb (Learning and Mathematics)  Sheila Tobias; Math Forum
In her 1990 book, They're Not Dumb, They're Different, Tobias addresses a concern that has been widely felt across the country for years: the shortfall in the number of students who go on to become scientists. She notes the importance of high school mathematics
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 Notes and Literature on Prime Numbers  Peter Alfeld, University of Utah
From Understanding Mathematics, a study guide for Univ. of Utah students. Includes definitions, explanations, links to other related sites, and a list of works to consult for further reference.
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 Notes for College Algebra and Geometry  M. Maheswaran, Univ. of WisconsinMarathon Center (UWMC)
A set of notes for students taking college algebra and geometry. Contents: Solving Applied ("Word") Problems; Solving Absolute Value Inequalities; Solving Rational Inequalities; Graphing Rational Functions; Graphing Conic Sections.
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 Notes on Linear Algebra  E. Lee Lady; University of Hawaii
A collection of short handouts. Files are in PDF and DVI formats. Contents include: systems of linear equations in a nutshell, how to find the inverse of a matrix, some equivalent statements, some equivalent characterizations of basic concepts, a "grammar
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 Not So Standard Deviations  Peng, Roger; and Parker, Hilary
Podcasts on the latest in data science and data analysis in academia and industry. Audio of conversations, which usually run 50 minutes and date back to October, 2015, have included "Gilmore Girls," "A Gajillion Time Series," "Google is the New Fisher,"
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 (Not) Tiling a Triangle of Dots  Don West, Department of Mathematics, SUNY Plattsburgh
A triangular array of dots can never be tiled by threeinline tiles, and
can be tiled by threeinatriangle tiles only if the size of the array is
congruent to 0, 2, 9, or 11 (mod 12). The author gives an elementary proof of these two results, not
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 NOVA Online: Hunting the Hidden Dimension  Public Broadcasting System (PBS)
The PBS television series NOVA has produced a program about fractals, their impact on the world of mathematics, and the way they're shaping our understanding of nature. In addition to the program itself (in five chapters), the website offers a program
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 NOVA Online: The Proof  WGBH, Public Broadcasting System (PBS)
For over 350 years, some of the greatest minds of science struggled to prove what was known as Fermat's Last Theorem  the idea that a certain simple equation had no solutions. This site includes an interview with Andrew Wiles (the man who spent seven
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 NOVA Podcasting  Public Broadcasting System (PBS)
Podcasts from the producers of the awardwinning science documentary show: NOVA Podcast: expanding on topics from the T.V. programs; NOVA scienceNOW podcast: conversations with scientists and science journalists; NOVA Vodcast: video podcasts; NOVA E
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 The Novel Polyhedra of Albert P. Carpenter  Albert P. Carpenter
A series of videos of slides exploring Exploded, Crown, Open and Lattice Polyhedra. See also Carpenter's YouTube channel of Structural Geometric Topology.
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 Nowhere Monotonic Continuous Function  Michal Wojcik
Proof of the existence of a continuous function f:[0,1]>R that is neither increasing nor decreasing on any subinterval of [0,1]. This proof uses the Baire Category Theorem.
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 NPComplete Arcade  John Lawrence
Site contains a number of applets that can be used to explore the circumstances under which some NPcomplete problems become hard.
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 The N Queens Problem  Marty Hall
Finding a solution to the NQueens problem for any N greater than or equal to 4 can be done without searching. Determining where each queen should go can be done in constant time per queen, or O(N) altogether. Thus, drawing the board (which is O(N^2))
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 The Nth Prime Page  Andrew Booker
A form into which you can enter a value for n, from 1 to 10^12, inclusive. The server will return the nth prime number (counting 2 as the first). Commas and scientific notation (e.g. 1.0e12) are allowed. Also a Pi function: enter a value for x, from 1
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 NT Number Theory (Front for the Mathematics ArXiv)  Univ. of California, Davis
Number Theory preprints, from the U.C. Davis front end for the xxx.lanl.gov ePrint archive, a major site for mathematics preprints that has incorporated many formerly independent specialist archives. Search by keyword or browse by topic.
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 Null Science  Bruce Bower  Science News Online
A growing number of psychologists charge that their field needs to wean itself from the mindless application of certain statistical practices, especially a technique known as null hypothesis or significance testing, where the investigator typically gathers
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 numb3rs blog  Mark Bridger, Department of Mathematics, Northeastern University
A blog where math professor Bridger posts mathematical comments on the TV show "Numb3rs". Dating back to February, 2005, posts include "Math and March Madness" and "Random motion and FokkerPlanck" and "Acoustic fingerprints and the JFK assassination"
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 NUMB3RS  CBS Broadcasting Inc.
NUMB3RS depicts how the confluence of police work and mathematics helps solve criminal questions. Watch video clips of actors Rob Morrow and David Krumholtz on the set, as well as trailers of the television show and previews of upcoming episodes.
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 Numb3rs Math Activities  Cornell Department of Mathematics
Notes and activities on the mathematics behind each CBS television broadcast of the FBI crime series NUMB3RS, from the pilot episode through season five: Uncertainty Principle, Sniper Zero, Dirty Bomb, Assassin, Toxin, Backscatter, Two Daughters, Burn
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 NumberADay  The Mathematical Association of America (MAA)
Every working day, a new positive integer, with a selection of its properties and an illustration or photograph.
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 Number Dictionary  Gerardis Giannis, Tsibourakis Dimitris
Enter a number to see its characteristics, such as primality, Fibonacci numbers, factorization, sum of first primes, sum of two squares, triangular numbers, roots, perfect numbers, and more...
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 The Number Empire  Vitalii Vanovschi
Enter a positive integer up to 10^12, press the "Go!" button, and The Number Empire states  in yes/no format  whether you entered a prime number, a Bell number, a Catalan number, or a factorial. The same single click displays the integer written out
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 Number Gossip  Tanya Khovanova
Searchable database up to the number 10,000. Checks more than 40 fun predefined properties of numbers, and shows many original and unique properties of an input number. See also this math coach's math blog, lectures, and more from her home page.
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 numbermaze  Mike Reilly & Jenks Norwalk
A Sudokulike maze puzzle that uses the number pattern from a clock face, one through twelve. Link these numbers in either direction – clockwise or counterclockwise – through the maze to solve the puzzle. Read complete rules, path strategy, hints, and
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 The Number of Latin Rectangles [PDF]  Peter Doyle
A paper that shows how to generate an expression for the number of kline Latin rectangles for any k. The computational complexity of the resulting expression, as measured by the number of additions and multiplications required to evaluate it, is on the
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 Numberphile  Brady Haran
Playful primer videos "about numbers and stuff," typically less than ten minutes long. Watch mathematicians talk about Benford's Law, favourite numbers (in response to a poll conducted by Alex Bellos), spaghetti numbers, Curta calculator, vampire numbers,
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 Numberplay  The New York Times
Mathematical, logical and scientific puzzles, with solution "recaps." The posts, by Gary Antonick and Pradeep Mutalik, have included "Surreal Hat Tricks," "The Puzzles of Pickover," "Prime Rib at Hogwarts," "Nim for (a) Change," "Phi  The Magic and the
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 Number Puzzles  Erich's Puzzle Palace; Erich Friedman
Three crosswordgrid style puzzles, with numerical operations filled in. Can you fill in the numbers that work? Answers provided.
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 Number Recreations  Shyam Sunder Gupta
Recreational aspects of number theory, prime numbers, and the like. Currently includes rare numbers, EPORNS (Equal Product Of Reversible Numbers), unique numbers, unlucky 13, fascinating squares, curious properties of 153, and amicable numbers (including
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 Number Server  Ben Coffey
A RESTlike service offering a variety of data for decimal and binary numbers: enter a number and get its sine, cosine, tangent, natural logarithm, square root, square, cube, binary, hexadecimal, octal, the singledigit sum of the digits, and more. Output
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 Numbers from 1 to 10 in Over 4000 Languages  Mark Rosenfelder
Click on the map to move to the languages for that area, or select from: IndoEuropean, Dravidian, and minor European languages; AfroAsiatic, Caucasian, NiloSaharan, Kordofanian, and Khoisan languages; NigerCongo languages; Uralic, Altaic, Tai, AustroAsiatic
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 Numbers (Mathematics Archives)  University of Tennessee, Knoxville (UTK)
Links to sites about particular numbers; dates; palindromes; Gaussian integers; Carmichael numbers; continued fractions; e; Egyptian fractions, mathematics, and numerals; constants; Fermat; Fibonacci numbers; pi; large numbers, sequences, prime numbers,
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 NumberSpiral.com  Robert Sacks
Instructions, observations, formulas, and a glossary about number spirals, formed by writing the nonnegative integers on a ribbon, rolling it up with zero at the center, and arranging the spiral so all the perfect squares line up in a row on the right
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 Number System  Prof. Nam Sun Wang; Univ. of Maryland, College Park, MD
A handout from a course on Computer Methods in Chemical Engineering, detailing bit and byte definitions, number system background, and conversions among bases: binary, octal, decimal, and hexadecimal systems.
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 NumberTheoretic Hacks  David Eppstein, Theory Group, ICS, UC Irvine
Simple numbertheoretic algorithms. Egyptian Fractions  algorithms and references; C++ implementation of J. H. Conway's "nimber" arithmetic; C++ fast algorithm for computing 2adic inverse; C program for rational approximation of real numbers; Interference
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 Number Theory  Alex LópezOrtiz and the Sci.Math FAQ Team
Links to information on: Fermat's Last Theorem (History of Fermat's Last Theorem; What is the current status of FLT?; Related Conjectures; Did Fermat prove this theorem?), and Prime Numbers.
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 Number Theory Calculator  Bardesane: Giuseppe Merlino
A blog with free math programs for Windows: prime numbers, twin prime pairs, Goldbach conjecture, Collatz conjecture, Fibonacci numbers, N = x^2 + y^2, modpow (A^B mod. C), primality test, prime factors, divisors number and sum, Pascal's triangle, nextprime,
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 Number Theory Centres  Keith Matthews, Dept of Math, University of Queensland, Brisbane, Australia
An alphabetical list of links to international number theory groups and research centres.
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 Number theory  Dario Alpern
A collection of calculators, tables, and articles about number theory, with an applet that is able to factor large numbers and a quadratic diophantine equation solver.
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 Number Theory Foundation
A foundation for collecting donations from supporters of number theory and disbursing them to encourage research. Supporters have directed available funds towards activities in computational and combinatorial number theory, and also towards general number
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 Number Theory: Historical things  Keith Matthews, Dept. of Math, University of Queensland, Brisbane, Australia
Biographies of past number theorists and various items of historical interest, including prizes, photos, and mathematical family trees.
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