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

Author

Alois P. Heinz, Oct 27 2018

Keywords

• nonn

Links

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

Crossrefs

Column k=3 of A291680.

Programs

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);