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A177543 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, up, down, up, down. 2
1, 1, 2, 6, 24, 120, 720, 4768, 35968, 312064, 3004160, 31764480, 365798400, 4555499520, 61232590848, 882227765248, 13547017240576, 221038858829824, 3818608204709888, 69637156745773056, 1336921845773107200, 26947721453843251200, 569023211226594803712 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..175

FORMULA

a(n) ~ c * d^n * n!, where d = 0.9598365530271216889440240044515..., c = 1.2474579024498809739499621681... . - Vaclav Kotesovec, Jan 17 2015

MAPLE

b:= proc(u, o, t) option remember; `if`(t>6, 0, `if`(u+o+t<7, (u+o)!,

      add(b(u-j, o+j-1, [1, 3, 1, 5, 1, 7][t]), j=1..u)+

      add(b(u+j-1, o-j, [2, 2, 4, 2, 6, 2][t]), j=1..o)))

    end:

a:= n-> b(n, 0, 1):

seq(a(n), n=0..25);  # Alois P. Heinz, Oct 24 2013

CROSSREFS

Column k=42 of A242784.

Sequence in context: A152363 A152359 A152362 * A189842 A189271 A152366

Adjacent sequences:  A177540 A177541 A177542 * A177544 A177545 A177546

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

a(17)-a(22) from Alois P. Heinz, Oct 24 2013

STATUS

approved

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Last modified October 21 21:25 EDT 2021. Contains 348155 sequences. (Running on oeis4.)