cp's OEIS Frontend

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.

%I A321110 #6 Oct 27 2018 15:12:47
%S A321110 2,8,36,156,666,2860,12336,53518,233874,1029134,4559664,20335346,
%T A321110 91254770,411885192,1869127696,8524561158,39058221662,179724281242,
%U A321110 830256254372,3849435933628,17907743518356,83566689375980,391087227771308,1835146738581226,8632600618453808
%N 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.
%H A321110 Alois P. Heinz, <a href="/A321110/b321110.txt">Table of n, a(n) for n = 3..1000</a>
%p A321110 b:= proc(u, o, k) option remember; `if`(u+o=0, 1,
%p A321110       add(b(u-j, o+j-1, k), j=1..min(2, u))+
%p A321110       add(b(u+j-1, o-j, k), j=1..min(k, o)))
%p A321110     end:
%p A321110 a:= n-> (k-> b(0, n, k)-b(0, n, k-1))(3):
%p A321110 seq(a(n), n=3..30);
%Y A321110 Column k=3 of A291680.
%K A321110 nonn
%O A321110 3,1
%A A321110 _Alois P. Heinz_, Oct 27 2018