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A177524 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, down, down, down. 2
1, 1, 2, 6, 24, 120, 715, 4970, 39480, 352800, 3502800, 38255900, 455795100, 5883052500, 81774966000, 1217871018000, 19346879737625, 326549862671250, 5835951345093750, 110091785625495000, 2186122850020215000, 45580964489553559375, 995625115672520581250 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..170

FORMULA

a(n) ~ c * d^n * n!, where d = 0.9928637443921790380857377558103269268777241137790934589694993..., c = 1.0369478195304845650491426260146999487076420703190374702807322... . - Vaclav Kotesovec, Aug 29 2014

MAPLE

b:= proc(u, o, t) option remember; `if`(t>5, 0, `if`(u+o=0, 1,

      add(b(u-j, o+j-1, `if`(t=1, 1, t+1)), j=1..u)+

      add(b(u+j-1, o-j, 2), j=1..o)))

    end:

a:= n-> `if`(n=0, 1, add(b(j-1, n-j, 1), j=1..n)):

seq(a(n), n=0..25);  # Alois P. Heinz, Oct 21 2013

CROSSREFS

Columns k=16,30 of A242784.

Sequence in context: A177531 A121987 A324132 * A223905 A164872 A226437

Adjacent sequences:  A177521 A177522 A177523 * A177525 A177526 A177527

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

a(17)-a(22) from Alois P. Heinz, Oct 20 2013

STATUS

approved

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Last modified October 16 02:52 EDT 2019. Contains 328038 sequences. (Running on oeis4.)