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

4,1

Links

Alois P. Heinz, Table of n, a(n) for n = 4..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))(4):
seq(a(n), n=4..30);

Crossrefs

Column k=4 of A291680.

Sequence in context: A365226 A263965 A265084 * A319321 A321574 A377583

Adjacent sequences: A321108 A321109 A321110 * A321112 A321113 A321114

Keyword

nonn

Author

Alois P. Heinz, Oct 27 2018

Status

approved