OFFSET
1,3
COMMENTS
LINKS
E. Deutsch and W. P. Johnson, Create your own permutation statistics, Math. Mag., 77, 130-134, 2004.
R. Simion and F. W. Schmidt, Restricted permutations, European J. Combin., 6, 383-406, 1985.
FORMULA
T(n, k) = n!k/[2(k-2)!(k+1)] for k<n; T(n, n) = n(n-1)/2.
EXAMPLE
T(3,2)=2 because only 132 and 321 satisfy the requirements.
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Emeric Deutsch, Apr 12 2004
STATUS
approved