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 A205403 #11 Dec 06 2021 13:23:56 %S A205403 1,2,1,2,1,4,2,1,2,2,1,3,6,2,1,3,2,2,1,7,3,8,2,1,4,3,5,2,1,4,9,3,5,2, %T A205403 1,4,6,3,9,2,1,10,4,6,3,15,2,1,2,4,10,3,3,2,1,7,15,4,20,3,8,2,1,11,7, %U A205403 4,5,3,6,2,1,5,11,7,4,14,3,6,2,1 %N A205403 a(n) is the index j < k such that n divides s(k)-s(j) for some j, where s(j) = floor((j+1)^2/2)/2, and k is the least index for which such a j exists. %C A205403 For a guide to related sequences, see A204892. %t A205403 (See the program at A205402.) %Y A205403 Cf. A205402, A204892. %K A205403 nonn %O A205403 1,2 %A A205403 _Clark Kimberling_, Jan 27 2012 %E A205403 Definition corrected by _Clark Kimberling_, Dec 05 2021