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 A177529 Number of permutations of {1,...,n} avoiding adjacent step pattern up, down, up, down, up. 2
 1, 1, 2, 6, 24, 120, 659, 4186, 31457, 264834, 2465550, 25334981, 283322383, 3430384284, 44803783445, 626719448981, 9347396890481, 148174002240074, 2486833885400060, 44052337160572208, 821495697573151302, 16085109561896603059, 329939476998354570978 (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 = 0.9323832531422843725281328190771918152..., c = 1.369593476632786981162993013559816... . - Vaclav Kotesovec, Jan 17 2015 MAPLE b:= proc(u, o, t) option remember; `if`(t>5, 0, `if`(u+o+t<6, (u+o)!, add(b(u-j, o+j-1, [1, 3, 1, 5, 1][t]), j=1..u)+ add(b(u+j-1, o-j, [2, 2, 4, 2, 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 MATHEMATICA b[u_, o_, t_] := b[u, o, t] = If[t > 5, 0, If[u + o + t < 6, (u + o)!, Sum[b[u - j, o + j - 1, {1, 3, 1, 5, 1}[[t]]], {j, 1, u}] + Sum[b[u + j - 1, o - j, {2, 2, 4, 2, 6}[[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=21 of A242784. Sequence in context: A152346 A152336 A152343 * A138619 A189841 A189256 Adjacent sequences: A177526 A177527 A177528 * A177530 A177531 A177532 KEYWORD nonn AUTHOR R. H. Hardin, May 10 2010 STATUS approved

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Last modified September 23 17:42 EDT 2023. Contains 365554 sequences. (Running on oeis4.)