A250287 Number of permutations p of [n] such that p(i) > p(i+1) iff i == 0 (mod 10).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 10, 65, 285, 1000, 3002, 8007, 19447, 43757, 92377, 184755, 3527140, 42031760, 326057040, 1961245375, 9812764391, 42530831916, 164059546366, 574224816166, 1850302218766, 5550936701311, 156435448534980, 2711548312208295

Offset

0,12

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=0, 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(n, 0$2):
seq(a(n), n=0..35);

Mathematica

nmax = 30; CoefficientList[Series[1 + Sum[(x^(10 - k) * HypergeometricPFQ[{1}, {11/10 - k/10, 6/5 - k/10, 13/10 - k/10, 7/5 - k/10, 3/2 - k/10, 8/5 - k/10, 17/10 - k/10, 9/5 - k/10, 19/10 - k/10, 2 - k/10}, -x^10/10000000000])/(10 - k)!, {k, 0, 9}] / HypergeometricPFQ[{}, {1/10, 1/5, 3/10, 2/5, 1/2, 3/5, 7/10, 4/5, 9/10}, -x^10/10000000000], {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Apr 21 2021 *)

Crossrefs

Row n=10 of A181937.

Sequence in context: A210369 A058920 A263472 * A059598 A327388 A341387

Adjacent sequences: A250284 A250285 A250286 * A250288 A250289 A250290

Keyword

nonn

Author

Alois P. Heinz, Nov 16 2014

Status

approved