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A250266 Number of permutations p of [n] such that p(i) > p(i+1) iff i=1 (mod 10). 2
1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 109, 768, 3627, 13636, 43665, 123744, 318223, 755802, 1679581, 3527140, 70542781, 878845662, 7113969943, 44573747024, 231938007625, 1043938332476, 4176060103827, 15138650342428, 50462774778029, 156435448534980 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..500

MAPLE

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

     `if`(t=1, add(b(u-j, o+j-1, irem(t+1, 10)), j=1..u),

               add(b(u+j-1, o-j, irem(t+1, 10)), j=1..o)))

    end:

a:= n-> b(0, n, 0):

seq(a(n), n=0..35);

MATHEMATICA

b[u_, o_, t_] := b[u, o, t] = If[u + o == 0, 1, If[t == 1, Sum[b[u - j, o + j - 1, Mod[t + 1, 10]], {j, 1, u}], Sum[b[u + j - 1, o - j, Mod[t + 1, 10]], {j, 1, o}]]];

a[n_] := b[0, n, 0];

Table[a[n], {n, 0, 35}] (* Jean-Fran├žois Alcover, Jul 22 2019, after Alois P. Heinz *)

CROSSREFS

Column k=10 of A250261.

Sequence in context: A111705 A071274 A258373 * A085908 A110304 A043315

Adjacent sequences:  A250263 A250264 A250265 * A250267 A250268 A250269

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Nov 15 2014

STATUS

approved

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Last modified June 25 03:04 EDT 2021. Contains 345449 sequences. (Running on oeis4.)