A226284 a(n) = [n/2]!*[(n+1)/2]!*C([n/2],3)*C([(n+1)/2],3).

0, 0, 0, 0, 0, 36, 576, 9216, 115200, 1440000, 17280000, 207360000, 2540160000, 31116960000, 398297088000, 5098202726400, 68825736806400, 929147446886400, 13273534955520000, 189621927936000000, 2868031660032000000, 43378978857984000000, 694063661727744000000

Offset: 1

Author

R. H. Hardin, connection of formula with combinatoric problem via N. J. A. Sloane in the Sequence Fans Mailing List, Jun 02 2013

Keywords

• nonn

Comments

Number of permutations of n elements with 6 odd displacements.

Column 4 of A226288.

Column k=6 of A145893, a diagonal of A145894. - Alois P. Heinz, May 29 2014

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A145893, A145894, A226288.

Programs

Mathematica

Table[Floor[n/2]!Floor[(n+1)/2]!Binomial[Floor[n/2],3]Binomial[Floor[ (n+1)/2], 3],{n,30}] (* Harvey P. Dale, Dec 12 2018 *)