A321066 Number of ordered pairs (p,q) of permutations of [n] with equal up-down signatures and p(1)=q(1)=10.

1035227008, 48904686848, 2945846638464, 218405906177792, 19438574276705792, 2038137238577944576, 248048061418810109952, 34621419911316556017664, 5486719044572824902107136, 978934483626207520876986368, 195206678980725195413273903104

Offset: 10

Author

Alois P. Heinz, Oct 26 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 10..110

Crossrefs

Column k=10 of A262372.

Programs

Maple

b:= proc(u, o, h) option remember; `if`(u+o=0, 1,
      add(add(b(u-j, o+j-1, h+i-1), i=1..u+o-h), j=1..u)+
      add(add(b(u+j-1, o-j, h-i), i=1..h), j=1..o))
    end:
a:= n-> (k-> b(k-1, n-k, n-k))(10):
seq(a(n), n=10..20);