cp's OEIS Frontend

A229891 Number of 10 up, 10 down permutations of [n].

%I A229891 #9 Oct 04 2013 07:44:22
%S A229891 1,1,1,1,1,1,1,1,1,1,1,1,11,66,286,1001,3003,8008,19448,43758,92378,
%T A229891 184756,3711916,39277446,290971966,1693270006,8237327526,34822561201,
%U A229891 131333661601,450356465701,1424215551901,4199713947571,122741742741301,1863639732429616
%N A229891 Number of 10 up, 10 down permutations of [n].
%H A229891 Alois P. Heinz, <a href="/A229891/b229891.txt">Table of n, a(n) for n = 0..200</a>
%p A229891 b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(`if`(t=10,
%p A229891        b(o-j, u+j-1, 1), b(u+j-1, o-j, t+1)), j=1..o))
%p A229891     end:
%p A229891 a:= n-> b(0, n, 0):
%p A229891 seq(a(n), n=0..35);
%Y A229891 Column k=10 of A229892.
%K A229891 nonn,eigen
%O A229891 0,13
%A A229891 _Alois P. Heinz_, Oct 02 2013