The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A177552 Number of permutations of {1,...,n} avoiding adjacent step pattern up, up, up, down, down, down. 2
 1, 1, 2, 6, 24, 120, 720, 5020, 40000, 358560, 3571200, 39124800, 467596800, 6054250840, 84417778720, 1261161277200, 20097223449600, 340275330912000, 6100262355686400, 115437689217984148, 2299445555596421920, 48093671993708346480, 1053794989665442654080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..200 FORMULA a(n) ~ c * d^n * n!, where d = 0.9959682894155038013878176356538407492626252741099726077392745662726589922..., c = 1.02468007512189851788618819144905616307144561621610927886626291999589... . - 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, 1, 1, 5, 6, 7][t]), j=1..u)+ add(b(u+j-1, o-j, [2, 3, 4, 4, 2, 2][t]), j=1..o))) end: a:= n-> b(n, 0, 1): seq(a(n), n=0..25); # Alois P. Heinz, Oct 30 2013 MATHEMATICA b[u_, o_, t_] := b[u, o, t] = If[t > 6, 0, If[u + o + t < 7, (u + o)!, Sum[b[u - j, o + j - 1, {1, 1, 1, 5, 6, 7}[[t]]], {j, 1, u}] + Sum[b[u + j - 1, o - j, {2, 3, 4, 4, 2, 2}[[t]]], {j, 1, o}]]]; a[n_] := b[n, 0, 1]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Apr 19 2022, after Alois P. Heinz *) CROSSREFS Column k=56 of A242784. Sequence in context: A324139 A324138 A324137 * A177547 A324136 A177548 Adjacent sequences: A177549 A177550 A177551 * A177553 A177554 A177555 KEYWORD nonn AUTHOR R. H. Hardin, May 10 2010 EXTENSIONS a(17)-a(22) from Alois P. Heinz, Oct 30 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 31 19:20 EDT 2023. Contains 361672 sequences. (Running on oeis4.)