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 A209573 #6 Feb 27 2013 09:44:12 %S A209573 1,1,1,2,4,1,3,9,9,1,4,17,29,16,1,5,28,69,74,25,1,6,42,138,224,160,36, %T A209573 1,7,59,245,541,613,307,49,1,8,79,399,1127,1781,1469,539,64,1,9,102, %U A209573 609,2111,4331,5103,3171,884,81,1,10,128,884,3649,9281,14419 %N A209573 Triangle of coefficients of polynomials u(n,x) jointly generated with A209574; see the Formula section. %C A209573 For n>1, let r(n,k) be the k-th number in row n. Then %C A209573 r(n,1)=n-1, r(n,n-1)=(n-1)^2, and r(n,n)=1. For a %C A209573 discussion and guide to related arrays, see A208510. %F A209573 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209573 v(n,x)=2x*u(n-1,x)+(x+1)*v(n-1,x)+1, %F A209573 where u(1,x)=1, v(1,x)=1. %e A209573 First five rows: %e A209573 1 %e A209573 1...1 %e A209573 2...4....1 %e A209573 3...9....9....1 %e A209573 4...17...29...16...1 %e A209573 First three polynomials v(n,x): 1, 1 + x, 2 + 4x + x^2. %t A209573 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209573 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209573 v[n_, x_] := 2 x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209573 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209573 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209573 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209573 TableForm[cu] %t A209573 Flatten[%] (* A209573 *) %t A209573 Table[Expand[v[n, x]], {n, 1, z}] %t A209573 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209573 TableForm[cv] %t A209573 Flatten[%] (* A209574 *) %Y A209573 Cf. A209574, A208510. %K A209573 nonn,tabl %O A209573 1,4 %A A209573 _Clark Kimberling_, Mar 11 2012