OFFSET
0,4
LINKS
Sean A. Irvine, Table of n, a(n) for n = 0..45
EXAMPLE
12 valid permutations for a(5): 12345 12354 12435 12453 12534 12543 13245 13254 13524 15234 15243 15324.
CROSSREFS
KEYWORD
nonn
AUTHOR
David W. Wilson, Jun 07 2000
STATUS
approved