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 A207617 #9 Mar 31 2023 03:22:21 %S A207617 1,2,1,3,3,4,7,1,5,14,5,6,25,16,1,7,41,41,7,8,63,91,29,1,9,92,182,92, %T A207617 9,10,129,336,246,46,1,11,175,582,582,175,11,12,231,957,1254,550,67,1, %U A207617 13,298,1507,2508,1507,298,13,14,377,2288,4719,3718,1079,92,1 %N A207617 Triangle of coefficients of polynomials v(n,x) jointly generated with A207616; see the Formula section. %F A207617 u(n,x)=u(n-1,x)+v(n-1,x), v(n,x)=xu(n-1,x)+v(n-1,x)+1, where u(1,x)=1, v(1,x)=1. %e A207617 First five rows: %e A207617 1 %e A207617 2...1 %e A207617 3...3 %e A207617 4...7...1 %e A207617 5...14...5 %t A207617 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A207617 u[n_, x_] := u[n - 1, x] + v[n - 1, x] %t A207617 v[n_, x_] := x*u[n - 1, x] + v[n - 1, x] + 1 %t A207617 Table[Factor[u[n, x]], {n, 1, z}] %t A207617 Table[Factor[v[n, x]], {n, 1, z}] %t A207617 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A207617 TableForm[cu] %t A207617 Flatten[%] (* A207616 *) %t A207617 Table[Expand[v[n, x]], {n, 1, z}] %t A207617 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A207617 TableForm[cv] %t A207617 Flatten[%] (* A207617 *) %Y A207617 Cf. A207616. %K A207617 nonn,tabf %O A207617 1,2 %A A207617 _Clark Kimberling_, Feb 20 2012