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 A256261 #15 Apr 19 2015 22:26:56 %S A256261 1,4,4,12,4,12,20,28,4,12,20,28,20,44,68,60,4,12,20,28,20,44,68,60,20, %T A256261 44,68,92,116,140,164,124,4,12,20,28,20,44,68,60,20,44,68,92,116,140, %U A256261 164,124,20,44,68,92,116,140,164,188,212,236,260,284,308,332,356,252,4,12,20,28,20,44,68,60,20,44,68,92,116,140 %N A256261 First differences of A256260. %C A256261 First 27 terms agree with A169708. Both sequences share infinitely many terms. %H A256261 N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a> %H A256261 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a> %F A256261 a(n) = 4*A256263(n), n >= 1. %e A256261 Written as an irregular triangle in which the row lengths are the terms of A011782, the sequence begins: %e A256261 1; %e A256261 4; %e A256261 4,12; %e A256261 4,12,20,28; %e A256261 4,12,20,28,20,44,68,60; %e A256261 4,12,20,28,20,44,68,60,20,44,68,92,116,140,164,124; %e A256261 4,12,20,28,20,44,68,60,20,44,68,92,116,140,164,124,20,44,68,92,116,140,164,188,212,236,260,284,308,332,356,252; %e A256261 ... %e A256261 It appears that the row sums give A000302. %e A256261 It appears that the right border gives A173033. %Y A256261 Cf. A000302, A011782, A139251, A147582, A169708, A173033, A256258, A256251, A256260, A256263, A256264, A256265. %K A256261 nonn,tabf %O A256261 0,2 %A A256261 _Omar E. Pol_, Mar 30 2015