A208905 Triangle of coefficients of polynomials u(n,x) jointly generated with A208906; see the Formula section.

1, 1, 2, 1, 6, 2, 1, 12, 6, 4, 1, 20, 12, 20, 4, 1, 30, 20, 60, 20, 8, 1, 42, 30, 140, 60, 56, 8, 1, 56, 42, 280, 140, 224, 56, 16, 1, 72, 56, 504, 280, 672, 224, 144, 16, 1, 90, 72, 840, 504, 1680, 672, 720, 144, 32, 1, 110, 90, 1320, 840, 3696, 1680, 2640, 720

Offset: 1

Author

Clark Kimberling, Mar 03 2012

Keywords

• nonn
• tabl

Comments

For a discussion and guide to related arrays, see A208510.

Examples

			First five rows:
1
1...2
1...6....2
1...12...6....4
1...20...12...20...4
First five polynomials u(n,x):
1
1 + 2x
1 + 6x + 2x^2
1 + 12x + 6x^2 + 4x^3
1 + 20x + 12x^2 + 20x^3 + 4x^4
		

Crossrefs

Cf. A208906, A208510.

Programs

Mathematica

u[1, x_] := 1; v[1, x_] := 1; z = 16;
u[n_, x_] := u[n - 1, x] + 2 x*v[n - 1, x];
v[n_, x_] := x*u[n - 1, x] + v[n - 1, x] + 1;
Table[Expand[u[n, x]], {n, 1, z/2}]
Table[Expand[v[n, x]], {n, 1, z/2}]
cu = Table[CoefficientList[u[n, x], x], {n, 1, z}];
TableForm[cu]
Flatten[%]  (* A208905 *)
Table[Expand[v[n, x]], {n, 1, z}]
cv = Table[CoefficientList[v[n, x], x], {n, 1, z}];
TableForm[cv]
Flatten[%]  (* A208906 *)

Formula

u(n,x)=u(n-1,x)+2x*v(n-1,x),

v(n,x)=x*u(n-1,x)+v(n-1,x)+1,

where u(1,x)=1, v(1,x)=1.