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 A179512 #2 Mar 30 2012 17:31:29 %S A179512 12,13,15,17,25,47,117,409,1985,13269,116555,1301043,17911307, %T A179512 296651169,5792367991,131137897895,3395020992813,99343099511585 %N A179512 a(1) = 12, a(n) = prime(a(n-1)) - 2a(n-1). %t A179512 NestList[ Prime@# - 2# &, 12, 17] %Y A179512 Cf. A007097, A074271, A179274, A179511, A179513, A179514, A179515, A179516, A179517, A179518. %K A179512 nonn %O A179512 1,1 %A A179512 _Robert G. Wilson v_, Jul 17 2010