Writing a Program to Generate PrimesDate: 12/5/95 at 17:21:52 From: Anonymous Subject: prime numbers I need a list of the first 100 prime numbers and a way of generating them. I hope you will help me! Thank you, Bonnie Thurber Date: 3/17/96 at 22:47:6 From: Doctor Jodi Subject: Re: prime numbers There is a list of first 10,000 primes at http://www.utm.edu/research/primes/lists/small/10000.txt -Doctor Jodi, The Math Forum Date: 3/20/96 at 0:36:45 From: Doctor Patrick Subject: Re: prime numbers Hi-- The first 100 primes are 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199 211 223 227 229 233 239 241 251 257 263 269 271 277 281 283 293 307 311 313 317 331 337 347 349 353 359 367 373 379 383 389 397 401 409 419 421 431 433 439 443 449 457 461 463 467 479 487 491 499 503 509 521 523 541. The easiest way to generate them is to use a computer program which tests each number to see if it can be factored by any number up to and including that number's square root. You can stop at the square root, since all other combinations of factors would include one number larger than the square root, and one smaller. Once you have gone through the smaller numbers it would be redundant to check the larger halves as well. Actually, you would only have to check a number by all of the primes up to its square root (Do you understand why?), but that would take more programming skill than I have at the moment. If you need more detailed information, take a look at http://www.utm.edu/research/primes/prove/ I'm attaching the program I used to find these 100 primes. It's written in c++, but uses entirely straight c, except for the sqrt() function. #include <stdio.h> #include <math.h> main () { int num, count, i, prime; num =2; for (count=0; count<100; num++) { /* keep track of primes found, stop at 100, increase the value of the number tested */ prime=1; /* prime keeps track of if a number is found to be prime or not--1=prime 0=not prime /* for (i=2; i<=sqrt(num); i++) if (num%i==0) prime=0; /*test to see in num is prime */ if (prime!=0) { printf("%d ", num); /* print primes */ count++;} /* inclease count of primes found */ } } -Doctor Patrick, The Math Forum |
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