OFFSET
1,3
COMMENTS
Number of permutations of n elements with 2 odd displacements.
Column 2 of A226288.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
MATHEMATICA
Table[Floor[n/2]!Floor[(n+1)/2]!Binomial[Floor[n/2], 1]Binomial[Floor[(n+1)/2], 1], {n, 30}] (* Harvey P. Dale, Aug 05 2023 *)
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