login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A177526 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, down, up, down. 2
1, 1, 2, 6, 24, 120, 680, 4480, 33600, 285434, 2684680, 27812170, 313926560, 3842611240, 50625902600, 714873188122, 10764733339179, 172258243070682, 2918333808555034, 52191694000877878, 982479378895814520, 19419959862935129834, 402131210857811703926 (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 = 0.94123983763344712685016041467..., c = 1.3558011859159420827133973526... . - 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, 6][t]), j=1..u)+

      add(b(u+j-1, o-j, [2, 2, 2, 5, 2][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=18,22 of A242784.

Sequence in context: A152340 A152347 A228393 * A214611 A177528 A177527

Adjacent sequences:  A177523 A177524 A177525 * A177527 A177528 A177529

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 15 06:24 EST 2019. Contains 329144 sequences. (Running on oeis4.)