A177554 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down.

1, 4, 28, 304, 4576, 91072, 2306176, 71993344, 2707268608, 120392433664, 6235322515456, 371376015818752, 25166910597922816, 1922787147517394944, 164313634414773403648

Offset

1,2

Links

Table of n, a(n) for n=1..15.

Crossrefs

Sequence in context: A007152 A345248 A295258 * A316212 A337592 A192485

Adjacent sequences: A177551 A177552 A177553 * A177555 A177556 A177557

Keyword

nonn

Author

R. H. Hardin, May 10 2010

Extensions

a(12)-a(15) from Alois P. Heinz, Oct 22 2013

Status

approved