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.

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A349727 Triangle read by rows, T(n, k) = [x^(n - k)] hypergeom([-n, -1 + n], [-n], x).

Original entry on oeis.org

1, 0, 1, 1, 1, 1, 4, 3, 2, 1, 15, 10, 6, 3, 1, 56, 35, 20, 10, 4, 1, 210, 126, 70, 35, 15, 5, 1, 792, 462, 252, 126, 56, 21, 6, 1, 3003, 1716, 924, 462, 210, 84, 28, 7, 1, 11440, 6435, 3432, 1716, 792, 330, 120, 36, 8, 1, 43758, 24310, 12870, 6435, 3003, 1287, 495, 165, 45, 9, 1
Offset: 0

Views

Author

Peter Luschny, Nov 27 2021

Keywords

Examples

			Triangle starts:
[0] 1;
[1] 0,     1;
[2] 1,     1,    1;
[3] 4,     3,    2,    1;
[4] 15,    10,   6,    3,    1;
[5] 56,    35,   20,   10,   4,   1;
[6] 210,   126,  70,   35,   15,  5,   1;
[7] 792,   462,  252,  126,  56,  21,  6,   1;
[8] 3003,  1716, 924,  462,  210, 84,  28,  7,  1;
[9] 11440, 6435, 3432, 1716, 792, 330, 120, 36, 8, 1;
		

Crossrefs

Row sums: A088218, alternating row sums: A091526.
Central coefficients: binomial(3*n-2, n) (cf. A117671).
T(n, 0) = binomial(2*(n-1), n) (cf. A001791).
Cf. A257635.

Programs

  • Maple
    p := n -> hypergeom([-n, -1 + n], [-n], x):
    seq(seq(coeff(simplify(p(n)), x, n - k), k = 0..n), n = 0..10);
  • Mathematica
    (* rows[0..k], k[0..oo] *)
    r={};k=11;For[n=0,nDetlef Meya, Jun 26 2023 *)

A384261 a(n) = Product_{k=0..n-1} (2*n+k-1).

Original entry on oeis.org

1, 1, 12, 210, 5040, 154440, 5765760, 253955520, 12893126400, 741354768000, 47621141568000, 3379847863392000, 262662462526464000, 22183557976419840000, 2023140487449489408000, 198155371076302768128000, 20744817468539834621952000, 2311708772421640603275264000
Offset: 0

Views

Author

Seiichi Manyama, May 23 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = prod(k=0, n-1, 2*n+k-1);
    
  • Python
    from sympy import rf
    def a(n): return rf(2*n-1, n)
    
  • Sage
    def a(n): return rising_factorial(2*n-1, n)

Formula

a(n) = RisingFactorial(2*n-1,n).
a(n) = n! * [x^n] 1/(1 - x)^(2*n-1).
a(n) = n! * binomial(3*n-2,n).
D-finite with recurrence 2*(-2*n+3)*a(n) +3*(3*n-2)*(3*n-4)*a(n-1)=0. - R. J. Mathar, May 26 2025
Previous Showing 11-12 of 12 results.