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 A209572 #5 Mar 30 2012 18:58:15 %S A209572 1,1,3,1,3,5,1,3,11,7,1,3,11,29,9,1,3,11,41,61,11,1,3,11,41,129,111, %T A209572 13,1,3,11,41,153,339,183,15,1,3,11,41,153,523,771,281,17,1,3,11,41, %U A209572 153,571,1571,1569,409,19,1,3,11,41,153,571,2035,4161,2929,571,21 %N A209572 Triangle of coefficients of polynomials v(n,x) jointly generated with A209571; see the Formula section. %C A209572 Combinatorial limit of row n satisfies linear recurrence %C A209572 r(n)=4*r(n-1)-r(n-2) with r(1)=1 and r(2)=3. For a %C A209572 discussion and guide to related arrays, see A208510. %F A209572 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209572 v(n,x)=2x*u(n-1,x)+x*v(n-1,x) +1, %F A209572 where u(1,x)=1, v(1,x)=1. %e A209572 First five rows: %e A209572 1 %e A209572 1...3 %e A209572 1...3...5 %e A209572 1...3...11...7 %e A209572 1...3...11...29...9 %e A209572 First three polynomials v(n,x): 1, 1 + 3x , 1 + 3x + 5x^2. %t A209572 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209572 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209572 v[n_, x_] := 2 x*u[n - 1, x] + x*v[n - 1, x] + 1; %t A209572 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209572 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209572 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209572 TableForm[cu] %t A209572 Flatten[%] (* A209571 *) %t A209572 Table[Expand[v[n, x]], {n, 1, z}] %t A209572 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209572 TableForm[cv] %t A209572 Flatten[%] (* A209572 *) %Y A209572 Cf. A209571, A208510. %K A209572 nonn,tabl %O A209572 1,3 %A A209572 _Clark Kimberling_, Mar 11 2012