OFFSET
0,2
EXAMPLE
a(0) = 1: the empty word.
a(1) = 40320: abcdefgh, abcdefhg, abcdegfh, ..., hgfedbca, hgfedcab, hgfedcba, (all permutations of 8 letters).
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jun 23 2012
STATUS
approved