OFFSET
1,4
LINKS
Frank Schmidt and Rodica Simion, Card shuffling and a transformation on S_n, Aequationes Math. 44 (1992), no. 1, 11-34.
MAPLE
binomial(n-2, floor(n/2)-1) + floor((n-1)/2)*binomial(n-3, floor(n/2)-2);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved