A256880 n*n!/round(n/2).

1, 4, 9, 48, 200, 1440, 8820, 80640, 653184, 7257600, 73180800, 958003200, 11564467200, 174356582400, 2451889440000, 41845579776000, 671854030848000, 12804747411456000, 231125690776780800, 4865804016353280000

Offset

1,2

Links

Table of n, a(n) for n=1..20.

Formula

a(2n-1) = A052145(n).

a(2n) = 4*A002674(n) = 2*A010050(n) = 2^(n+1)*A000680(n), n>=1.

Prog

(PARI) a(n)=n*n!/round(n/2) \\ M. F. Hasler, Apr 22 2015

Crossrefs

Cf. A000142, A052145.

Sequence in context: A025558 A298986 A103933 * A327699 A013495 A164839

Adjacent sequences: A256877 A256878 A256879 * A256881 A256882 A256883

Keyword

nonn,easy

Author

M. F. Hasler, Apr 21 2015

Status

approved