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 A133431 #3 Mar 30 2012 16:50:43 %S A133431 1,2,3,4,5,7,10,11,12,14,15,18,24,25,26,28,29,31,33,35,38,39,42,43,46, %T A133431 49,50,53,56,59,63,64,67,68,75,81,82,87,89,91,92,94,96,106,109,120, %U A133431 124,126,129,130,137,141,143,148,154,157,158,159,165,166,171,172,173,176,180,185,186,187,192,194,196,197 %N A133431 Old-fashioned version of A002504 (the initial 1 should be omitted since 1 is no longer regarded as a prime, although it was in 1912). %D A133431 A. J. C. Cunningham, On quasi-Mersennian numbers, Mess. Math., 41 (1912), 119-146. %K A133431 nonn %O A133431 1,2 %A A133431 _N. J. A. Sloane_, Nov 28 2007