A161738 Sequence related to the column sums of the BG2 matrix

1, 1, 3, 15, 35, 315, 693, 9009, 19305, 328185, 692835, 14549535, 30421755, 760543875, 1579591125, 45808142625, 94670161425, 3124115327025, 6432002143875, 237984079323375, 488493636505875, 20028239096740875

Offset

1,3

Links

G. C. Greubel, Table of n, a(n) for n = 1..667

Formula

a(n) = product((2*n-3-2*k), k=0..floor(n/2-1)).

numer(a(n+2)/a(n+1)) = A005408(n) for n=>0.

denom(a(n+2)/a(n+1)) = A093178(n) for n=>0.

Mathematica

Table[Product[(2*n - 3 - 2*k), {k, 0, Floor[n/2 - 1]}], {n, 1, 50}] (* G. C. Greubel, Sep 26 2018 *)

Prog

(PARI) for(n=1, 50, print1(prod(k=0, floor(n/2 -1), 2*n-2*k-3), ", ")) \\ G. C. Greubel, Sep 26 2018
(Magma) [1] cat [(&*[2*n-2*k-3:k in [0..Floor(n/2 -1)]]): n in [2..50]]; // G. C. Greubel, Sep 26 2018

Crossrefs

Cf. A161736, A005408 and A093178.

Sequence in context: A347998 A162441 A001803 * A062741 A185541 A176661

Adjacent sequences: A161735 A161736 A161737 * A161739 A161740 A161741

Keyword

easy,nonn

Author

Johannes W. Meijer, Jun 18 2009

Status

approved