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

Author

M. F. Hasler, Apr 21 2015

Keywords

• nonn
• easy

Crossrefs

Cf. A000142, A052145.

Programs

PARI

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

Formula

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

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