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 A205139 #9 Feb 27 2013 09:44:11 %S A205139 1,1,1,1,3,2,2,5,1,3,1,4,4,4,2,5,2,1,6,3,1,7,3,4,1,9,1,2,4,2,10,21,6, %T A205139 1,5,1,12,14,3,3,6,8,14,4,4,2,7,4,6,1,10,7,8,2,5,2,5,3,9,12 %N A205139 The index j<k such that n divides s(k)-s(j), where k is the least index (A205138) for which such j exists, and s(k)=k*(3k-1)/2, the k-th pentagonal number. %C A205139 For a guide to related sequences, see A204892. %t A205139 (See the program at A205138.) %Y A205139 Cf. A205138, A204892. %K A205139 nonn %O A205139 1,5 %A A205139 _Clark Kimberling_, Jan 25 2012