login
A177556
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down.
0
1, 6, 78, 1735, 59246, 2885772, 190320239, 16347310234, 1774441830858, 237627036224047, 38497690772499518, 7423393488778249536, 1680457375599950641631, 441370935373373671881586
OFFSET
1,2
CROSSREFS
Sequence in context: A332680 A376093 A179498 * A219435 A219135 A208308
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 10 2010
EXTENSIONS
a(11)-a(14) from Alois P. Heinz, Nov 02 2013
STATUS
approved