A321111 Number of permutations p of [n] such that in 0p the largest up-jump equals four and no down-jump is larger than 2.

4, 20, 108, 586, 3098, 16230, 85150, 446972, 2349616, 12376800, 65353448, 345933358, 1835637246, 9764363438, 52064375292, 278256581910, 1490475179006, 8000983513636, 43039329754332, 231982689315468, 1252791611642654, 6777998215153164, 36735901427197962

Offset: 4

Author

Alois P. Heinz, Oct 27 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 4..1000

Crossrefs

Column k=4 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))(4):
seq(a(n), n=4..30);