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 A205142 #9 Apr 09 2015 16:34:46 %S A205142 4,4,21,4,10,30,7,16,144,10,11,48,13,70,30,16,17,144,19,80,21,22,23, %T A205142 48,50,130,1161,112,29,30,31,64,66,34,35,144,37,190,39,80,41,84,43, %U A205142 308,225,46,47,48,196,50,102,260,53,1242,110,112,57,58,59,120 %N A205142 s(k)-s(j), where (s(k),s(j)) is the least such pair for which n divides their difference, and s(j)=j(3j-1)/2, the j-th pentagonal number. %C A205142 For a guide to related sequences, see A204892. %t A205142 (See the program at A205138.) %Y A205142 Cf. A205138, A204892. %K A205142 nonn %O A205142 1,1 %A A205142 _Clark Kimberling_, Jan 25 2012