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A177540 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, down, up, up, down. 2
1, 1, 2, 6, 24, 120, 720, 4908, 38208, 334368, 3248640, 34774112, 405758208, 5129918808, 69849531936, 1018876044528, 15854497560576, 262116761475488, 4588408779868800, 84784281517177940, 1649073291620014880, 33678805727832427224, 720569710852319474016 (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 = 0.97251576612005359341988641793523250275..., c = 1.18354011206219905745522624899424386... . - 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, 4, 1, 3, 7][t]), j=1..u)+

      add(b(u+j-1, o-j, [2, 2, 2, 5, 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=38 of A242784.

Sequence in context: A177539 A177546 A177544 * A068201 A189848 A189285

Adjacent sequences:  A177537 A177538 A177539 * A177541 A177542 A177543

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 September 19 17:35 EDT 2021. Contains 347564 sequences. (Running on oeis4.)