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 A140957 #13 Feb 22 2020 20:57:36 %S A140957 2,2,1,4,1,1,8,1,1,2,16,2,1,1,4,32,4,1,1,2,8,64,8,2,1,1,4,16,128,16,4, %T A140957 1,1,2,8,32,256,32,8,2,1,1,4,16,64,512,64,16,4,1 %N A140957 a(n) = A140951(n+1) - A140951(n). %C A140957 All terms belong to A000079. %C A140957 Note that the positions of the first occurrences of 4, 8, 16, 32, 64, ... are 3, 6, 10, 15, 21, ... %C A140957 So a(n) can be displayed as a triangle (hence the tabl keyword), with row sums: 2, 3, 6, 12, 24, 48, ... = A042950. %C A140957 2; %C A140957 2, 1; %C A140957 4, 1, 1; %C A140957 8, 1, 1, 2; %C A140957 It can also be displayed as an irregular table, with length distribution: 1, 1, 3, 3, 5, 5, 7, 7, 9, 9 (doubled A005408) to get palindromic lines. %C A140957 2; %C A140957 2; %C A140957 1, 4, 1; %C A140957 1, 8, 1; %C A140957 1, 2, 16, 2, 1; %C A140957 1, 4, 32, 4, 1; %C A140957 with row sums: 2, 2, 6, 10, 22, 42, 66, 170, 342, 682, ... = A078008(n+2) = 2*A001045(n+1). %Y A140957 Cf. A000079, A042950, A140951, A140643. %K A140957 nonn,tabl %O A140957 0,1 %A A140957 _Paul Curtz_, Jul 26 2008 %E A140957 Edited by _Michel Marcus_, Jan 11 2012