A132911 a(n)=(n+1)(2n)!/2^n.

1, 2, 18, 360, 12600, 680400, 52390800, 5448643200, 735566832000, 125046361440000, 26134689540960000, 6585941764321920000, 1969196587532254080000, 689218805636288928000000

Offset

0,2

Comments

Define T(n,k)=((1+(-1)^n)/2)*C(k-1+n/2, n/2)*n!/2^(n/2). Then T(n,k) has e.g.f. 1/sum{j=0..k, C(k,j)*(-1)^j*x^(2j)/2^j}. T(n,1) is A000680 with interpolated zeros. T(n,3) is A132912.

Links

Table of n, a(n) for n=0..13.

Daniele Marchei, Emanuela Merelli, and Andrew Francis, Factorizing the Brauer monoid in polynomial time, arXiv:2402.07874 [math.RA], 2024. See p. 24.

Formula

E.g.f.: 1/(1-x^2+x^4/4) (with interpolated zeros);

a(n)-(n+1)*(2*n-1)*a(n-1)=0. - R. J. Mathar, Nov 05 2012

Mathematica

Table[(n+1) (2n)!/2^n, {n, 0, 20}] (* Harvey P. Dale, Jun 02 2020 *)

Crossrefs

Sequence in context: A123311 A349881 A181536 * A291902 A336217 A226837

Adjacent sequences: A132908 A132909 A132910 * A132912 A132913 A132914

Keyword

easy,nonn

Author

Paul Barry, Sep 04 2007

Status

approved