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 A209584 #5 Mar 30 2012 18:58:15 %S A209584 1,3,2,5,7,3,9,18,14,4,15,42,48,25,5,25,89,137,107,41,6,41,180,348, %T A209584 364,212,63,7,67,350,820,1078,844,386,92,8,109,663,1827,2902,2864, %U A209584 1773,659,129,9,177,1230,3906,7284,8692,6809,3453,1069,175,10,287 %N A209584 Triangle of coefficients of polynomials v(n,x) jointly generated with A209583; see the Formula section. %C A209584 Alternating row sums: 1,1,1,1,1,1,1,1,1,1,1,1,1,1,... %C A209584 For a discussion and guide to related arrays, see A208510. %F A209584 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209584 v(n,x)=(x+1)*u(n-1,x)+(x+1) %F A209584 where u(1,x)=1, v(1,x)=1. %e A209584 First five rows: %e A209584 1 %e A209584 3....1 %e A209584 5....7....3 %e A209584 9....18...14...4 %e A209584 15...42...48...25...5 %e A209584 First three polynomials v(n,x): 1, 3 + x , 5 + 7x + 3x^2. %t A209584 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209584 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209584 v[n_, x_] := (x + 1)*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209584 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209584 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209584 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209584 TableForm[cu] %t A209584 Flatten[%] (* A209583 *) %t A209584 Table[Expand[v[n, x]], {n, 1, z}] %t A209584 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209584 TableForm[cv] %t A209584 Flatten[%] (* A209584 *) %Y A209584 Cf. A209583, A208510. %K A209584 nonn,tabl %O A209584 1,2 %A A209584 _Clark Kimberling_, Mar 11 2012