This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A033809 #13 Mar 30 2014 04:54:20 %S A033809 1,1,1,2,1,1,2,1,3,6,1,1,2,2,1,8,1,1,2,1,1,2,2,583,2,1,1,4,2,5,4,1,1, %T A033809 2,1,3,2,1,3,2,1,1,4,2,1,8,2,1,2,1,3,16,1,3,6,1,1,2,3,1,8,6,1,2,3,1,4, %U A033809 1,3,2,1,53,6,8,3,4,1,1,8,6,3,2,1,7,2,8,1,2,2,1,4,1,3,6,1,1,2,4,15,2 %N A033809 Smallest m>0 such that (2n-1)2^m+1 is prime, or -1 if no such value exists. %C A033809 There exist odd integers 2k-1 such that (2k-1)2^n+1 is always composite. %D A033809 Ribenboim, P. The New Book of Prime Number Records. New York: Springer-Verlag, pp. 357-359, 1996. %H A033809 T. D. Noe, <a href="/A033809/b033809.txt">Table of n, a(n) for n=1..1000</a> %Y A033809 Cf. A046067 (except for initial term a(1) identical to this sequence), A046068, A046069, A046070. %Y A033809 Cf. A040076 %K A033809 sign %O A033809 1,4 %A A033809 _Eric W. Weisstein_