cp's OEIS Frontend

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.

A193860 Triangular array: the fission of ((2x+1)^n) by (q(n,x)), where q(n,x)=x^n+x^(n-1)+...+x+1.

Original entry on oeis.org

1, 1, 5, 1, 7, 19, 1, 9, 33, 65, 1, 11, 51, 131, 211, 1, 13, 73, 233, 473, 665, 1, 15, 99, 379, 939, 1611, 2059, 1, 17, 129, 577, 1697, 3489, 5281, 6305, 1, 19, 163, 835, 2851, 6883, 12259, 16867, 19171, 1, 21, 201, 1161, 4521, 12585, 26025, 41385, 52905
Offset: 0

Views

Author

Clark Kimberling, Aug 07 2011

Keywords

Comments

See A193842 for the definition of fission of two sequences of polynomials or triangular arrays.

Examples

			First six rows:
1
1...5
1...7....19
1...9....33...65
1...11...51...131...211
1...13...73...233...473...665
		

Crossrefs

Programs

  • Mathematica
    z = 10;
    p[n_, x_] := (2 x + 1)^n;
    q[0, x_] := 1; q[n_, x_] := x*q[n - 1, x] + 1;
    p1[n_, k_] := Coefficient[p[n, x], x^k];
    p1[n_, 0] := p[n, x] /. x -> 0;
    d[n_, x_] := Sum[p1[n, k]*q[n - 1 - k, x], {k, 0, n - 1}]
    h[n_] := CoefficientList[d[n, x], {x}]
    TableForm[Table[Reverse[h[n]], {n, 0, z}]]
    Flatten[Table[Reverse[h[n]], {n, -1, z}]]  (* A193860 *)
    TableForm[Table[h[n], {n, 0, z}]]
    Flatten[Table[h[n], {n, -1, z}]]   (* A193861  *)

Formula

From Peter Bala, Jul 16 2013: (Start)
T(n,k) = sum {i = 0..k} binomial(n+1,k-i)*2^(k-i) for 0 <= k <= n.
O.g.f.: 1/( (1 - 3*x*t)*(1 - (2*x + 1)*t) ) = 1 + (1 + 5*x)*t + (1 + 7*x + 19*x^2)*t^2 + ....
The n-th row polynomial R(n,x) = 1/(1 - x)*( (2*x + 1)^(n+1) - (3*x)^(n+1) ). Cf. A193823. (End)