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 A205131 #9 Feb 27 2013 09:44:11 %S A205131 1,1,2,1,1,3,1,1,2,3,2,2,3,1,3,1,4,1,4,2,5,2,5,3,6,9,1,7,7,3,7,1,8,12, %T A205131 3,5,9,4,2,5,10,6,10,1,1,5,11,2,2,4,3,8,13,6,6,5,2,21,14,2 %N A205131 The index j<k such that n divides s(k)-s(j), where k is the least index (A205130) for which such j exists, and s(k)=2*k^2-k, the k-th hexagonal number. %C A205131 For a guide to related sequences, see A204892. %t A205131 (See the program at A205130.) %Y A205131 Cf. A205130, A204892. %K A205131 nonn %O A205131 1,3 %A A205131 _Clark Kimberling_, Jan 25 2012