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Topic: [math-learn] can any one solve my challenge. lets see.
Replies: 3   Last Post: Dec 26, 2010 2:52 PM

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Ralph A. Raimi

Posts: 724
Registered: 12/3/04
Re: [math-learn] can any one solve my challenge. lets see.
Posted: Dec 26, 2010 2:52 PM
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On Sun, 26 Dec 2010, tcymark@yahoo.com wrote:

> what is the 88th term to this a.p. 4, 8, 12, 16......

I couldn't figure out what an "a.p." was, so I chose the nearest
convenient formula that produces these as the first four terms, and found:

If A(n) = 4n + (n-1)(n-2)(n-3)(n-4), I sure enough get
A(1) = 4*1 + 0*(-1)*(-2)*(-3), or 4*1;
A(2) = 4*2 + 1*(0)*(-1)*(-2), or 4*2;
A(3) = 4*3 + 2*1*0*(-1), or 4*3; and
A(4) = 4*4 + 3*2*1*0, or 4*4.

So we get the first four terms correct using this formula. Then

A(88) = 4*88 + 87*86*85*84, or 53421832.


Ralph A. Raimi Tel. 585 275 4429 or (home) 585 244 9368
Dept. of Mathematics, Univ. of Rochester, Rochester, NY 14627
<http://www.math.rochester.edu/people/faculty/rarm/>





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