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A177527 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, down, up, up. 2
1, 1, 2, 6, 24, 120, 694, 4676, 35952, 310464, 2984176, 31536583, 363591384, 4541789148, 61089594448, 880428095803, 13534614549829, 221066397540186, 3823205871530350, 69792946997645295, 1341134146478847104, 27059669661295560098, 571973335506443017436 (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 = 0.96079505301634594056671142147783512755736606..., c = 1.2266835832918378326758739778897107143678546... . - Vaclav Kotesovec, Jan 17 2015

MAPLE

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

      add(b(u-j, o+j-1, [1, 3, 4, 1, 3][t]), j=1..u)+

      add(b(u+j-1, o-j, [2, 2, 2, 5, 6][t]), 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=19,25 of A242784.

Sequence in context: A177526 A214611 A177528 * A068200 A189847 A189284

Adjacent sequences:  A177524 A177525 A177526 * A177528 A177529 A177530

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

a(17)-a(22) from Alois P. Heinz, Oct 21 2013

STATUS

approved

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Last modified November 19 16:37 EST 2019. Contains 329323 sequences. (Running on oeis4.)