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 A209566 #6 Mar 30 2012 18:58:15 %S A209566 1,1,3,1,3,7,1,3,10,15,1,3,10,31,31,1,3,10,34,88,63,1,3,10,34,113,233, %T A209566 127,1,3,10,34,116,359,586,255,1,3,10,34,116,393,1084,1419,511,1,3,10, %U A209566 34,116,396,1306,3120,3340,1023,1,3,10,34,116,396,1349,4216 %N A209566 Triangle of coefficients of polynomials v(n,x) jointly generated with A209565; see the Formula section. %C A209566 For a discussion and guide to related arrays, see A208510. %F A209566 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209566 v(n,x)=x*u(n-1,x)+2x*v(n-1,x) +1, %F A209566 where u(1,x)=1, v(1,x)=1. %e A209566 First five rows: %e A209566 1 %e A209566 1...1 %e A209566 1...4...1 %e A209566 1...4...11...1 %e A209566 1...4...14...26...1 %e A209566 First three polynomials v(n,x): 1, 1 + x , 1 + 4x + x^2 . %t A209566 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209566 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209566 v[n_, x_] := x*u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A209566 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209566 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209566 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209566 TableForm[cu] %t A209566 Flatten[%] (* A209565 *) %t A209566 Table[Expand[v[n, x]], {n, 1, z}] %t A209566 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209566 TableForm[cv] %t A209566 Flatten[%] (* A209566 *) %Y A209566 Cf. A209565, A208510. %K A209566 nonn,tabl %O A209566 1,3 %A A209566 _Clark Kimberling_, Mar 10 2012