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 A209574 #5 Mar 30 2012 18:58:15 %S A209574 1,2,3,3,7,5,4,14,20,7,5,24,52,45,9,6,37,110,155,86,11,7,53,203,403, %T A209574 389,147,13,8,72,340,882,1240,856,232,15,9,94,530,1712,3204,3322,1702, %U A209574 345,17,10,119,782,3040,7170,10088,7962,3125,490,19,11,147,1105 %N A209574 Triangle of coefficients of polynomials v(n,x) jointly generated with A209573; see the Formula section. %C A209574 Combinatorial limit of row n satisfies linear recurrence %C A209574 r(n)=4*r(n-1)-r(n-2) with r(1)=1 and r(2)=3. For a %C A209574 discussion and guide to related arrays, see A208510. %F A209574 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209574 v(n,x)=2x*u(n-1,x)+(x+1)*v(n-1,x)+1, %F A209574 where u(1,x)=1, v(1,x)=1. %e A209574 First five rows: %e A209574 1 %e A209574 2...3 %e A209574 3...7....5 %e A209574 4...14...20...7 %e A209574 5...24...52...45...9 %e A209574 First three polynomials v(n,x): 1, 2 + 3x , 3 + 7x + 5x^2. %t A209574 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209574 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209574 v[n_, x_] := 2 x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209574 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209574 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209574 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209574 TableForm[cu] %t A209574 Flatten[%] (* A209573 *) %t A209574 Table[Expand[v[n, x]], {n, 1, z}] %t A209574 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209574 TableForm[cv] %t A209574 Flatten[%] (* A209574 *) %Y A209574 Cf. A209573, A208510. %K A209574 nonn,tabl %O A209574 1,2 %A A209574 _Clark Kimberling_, Mar 11 2012