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From: gjk@talcott.UUCP (Greg Kuperberg)
Newsgroups: net.puzzle
Subject: Re: Re: > What comes next in the series 2, 3, 5, 7 ???
Message-ID: <428@talcott.UUCP>
Date: Thu, 2-May-85 01:43:55 EDT
Article-I.D.: talcott.428
Posted: Thu May  2 01:43:55 1985
Date-Received: Sat, 4-May-85 05:09:12 EDT
References: <1635@decwrl.UUCP> <282@mhuxh.UUCP>
Organization: Harvard University
Lines: 16

> I think the next numbers are: 10, 13, 16, 20, 24 ...
> Because from 2 to 3 is a step of 1 (there is one step of 1)
> from 3 to 5 and 5 to 7 are steps of 2 (there are two steps of 2).
> Therefore, I would expect three steps of 3 to follow, etc.
> Tom.

No, no, no!  The answer is obviously 8.  Why?  Let p(n)=2*n+1-(n-1)*(n-2)*
(n-3)/6.  p(0)=2, p(1)=3, p(2)=5, p(3)=7, and p(4)=8.

:-)
-- 
			Greg Kuperberg
		     harvard!talcott!gjk

"The eerily accurate drawing of Goetz showed the face of the 'before'
figure in comic-book ads for body-building devices."-Time Magazine, April 8