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 A256895 #6 Apr 29 2015 06:39:00 %S A256895 1,1,1,1,3,1,1,11,7,1,1,49,47,13,1,1,261,341,139,21,1,1,1631,2731, %T A256895 1471,329,31,1,1,11743,24173,16213,4789,671,43,1,1,95901,235463, %U A256895 189373,69441,12881,1231,57,1,1,876809,2509621,2357503,1032245,237961,30169,2087,73,1 %N A256895 Triangle read by rows, T(n,k) = Sum_{j=0..n-k+1} j!*C(n-1,j-1)*T(n-j,k-1) if k != 0 else 1, n>=0, 0<=k<=n. %C A256895 Can be understood as a convolution matrix or as a sequence-to-triangle transformation similar to the partial Bell polynomials defined as: S -> T(n, k, S) = Sum_{j=0..n-k+1} C(n-1,j-1)*S(j)*T(n-j,k-1,S) if k != 0 else S(0)^n. Here S(n) = n!. The case S(n) = n gives the triangle of idempotent numbers A059297 and the case S(n) = 1 for all n leads to A256894. %F A256895 T(n+1,1) = A001339(n) for n>=0. %F A256895 T(n,n-1) = A002061(n) for n>=1. %e A256895 Triangle starts: %e A256895 1; %e A256895 1, 1; %e A256895 1, 3, 1; %e A256895 1, 11, 7, 1; %e A256895 1, 49, 47, 13, 1; %e A256895 1, 261, 341, 139, 21, 1; %p A256895 # Implemented as a sequence transformation acting on f: n -> n!. %p A256895 F := proc(n, k, f) option remember; `if`(k=0, f(0)^n, %p A256895 add(binomial(n-1, j-1)*f(j)*F(n-j, k-1, f), j=0..n-k+1)) end: %p A256895 for n from 0 to 7 do seq(F(n, k, j->j!), k=0..n) od; %Y A256895 Cf. A001339, A002061, A059297, A256894. %K A256895 nonn,tabl,easy %O A256895 0,5 %A A256895 _Peter Luschny_, Apr 28 2015