A321110 Number of permutations p of [n] such that in 0p the largest up-jump equals three and no down-jump is larger than 2.

2, 8, 36, 156, 666, 2860, 12336, 53518, 233874, 1029134, 4559664, 20335346, 91254770, 411885192, 1869127696, 8524561158, 39058221662, 179724281242, 830256254372, 3849435933628, 17907743518356, 83566689375980, 391087227771308, 1835146738581226, 8632600618453808

Offset

3,1

Links

Alois P. Heinz, Table of n, a(n) for n = 3..1000

Maple

b:= proc(u, o, k) option remember; `if`(u+o=0, 1,
      add(b(u-j, o+j-1, k), j=1..min(2, u))+
      add(b(u+j-1, o-j, k), j=1..min(k, o)))
    end:
a:= n-> (k-> b(0, n, k)-b(0, n, k-1))(3):
seq(a(n), n=3..30);

Crossrefs

Column k=3 of A291680.

Sequence in context: A295501 A283847 A123290 * A228791 A088675 A228197

Adjacent sequences: A321107 A321108 A321109 * A321111 A321112 A321113

Keyword

nonn

Author

Alois P. Heinz, Oct 27 2018

Status

approved