OFFSET
1,8
COMMENTS
Number of permutations of n elements with 8 odd displacements.
Column 5 of A226288.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
MATHEMATICA
a[n_]:= Floor[n/2]!*Floor[(n+1)/2]!*Binomial[Floor[n/2], 4]*Binomial[Floor[(n+1)/2], 4]; Array[a, 21] (* Stefano Spezia, Jul 12 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, connection of formula with combinatoric problem via N. J. A. Sloane in the Sequence Fans Mailing List, Jun 02 2013
STATUS
approved