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 A125975 #5 Mar 31 2012 13:21:12 %S A125975 0,1,2,3,5,7,10,11,12,13,15,21,31,38,39,42,43,44,45,50,51,52,53,56,57, %T A125975 63,85,127,142,143,150,151,154,155,156,157,166,167,170,171,172,173, %U A125975 178,179,180,181,184,185,198,199,202,203,204,205,210,211,212,213,216 %N A125975 Integers i, for which A125974(A125974(i)) = i. %C A125975 The even terms seem to be the even terms of A031443 and some of the odd terms are produced by the composition A030101 o A014486. %K A125975 nonn,base %O A125975 0,3 %A A125975 _Antti Karttunen_, Jan 02 2007