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 A130266 #6 Feb 20 2022 14:45:25 %S A130266 1,1,2,4,1,3,2,5,1,4,7,2,6,1,5,3,8,2,7,1,6,10,3,9,2,8,1,7,4,11,3,10,2, %T A130266 9,1,8,13,4,12,3,11,2,10,1,9,5,14,4,13,3,12,2,11,1,10,16,5,15,4,14,3, %U A130266 13,2,12,1,11,6,17,5,16,4,15,3,14,2,13 %N A130266 A051340 * A128174. %C A130266 Row sums = A014255: (1, 3, 8, 12, 21, 27, 40, ...). %C A130266 Left border = A123684: (1, 1, 4, 2, 7, 3, 10, 4, ...). %F A130266 A051340 * A128174 as infinite lower triangular matrices. %e A130266 First few rows of the triangle: %e A130266 1; %e A130266 1, 2; %e A130266 4, 1, 3; %e A130266 2, 5, 1, 4; %e A130266 7, 2, 6, 1, 5; %e A130266 3, 8, 2, 7, 1, 6; %e A130266 10, 3, 9, 2, 8, 1, 7; %e A130266 ... %p A130266 A128174 := proc(n,k) %p A130266 if k > n or k < 1 then %p A130266 0; %p A130266 else %p A130266 modp(k+n+1,2) ; %p A130266 end if; %p A130266 end proc: %p A130266 A051340 := proc(n,k) %p A130266 if k = n then %p A130266 n ; %p A130266 elif k <= n then %p A130266 1; %p A130266 else %p A130266 0; %p A130266 end if; %p A130266 end proc: %p A130266 A130266 := proc(n,k) %p A130266 add( A051340(n,j)*A128174(j,k),j=k..n) ; %p A130266 end proc: %p A130266 seq(seq(A130266(n,k),k=1..n),n=1..15) ; # _R. J. Mathar_, Aug 06 2016 %Y A130266 Cf. A051340, A128174, A014255, A123684. %K A130266 nonn,tabl,easy %O A130266 0,3 %A A130266 _Gary W. Adamson_, May 18 2007