%I #9 Oct 04 2013 07:05:39
%S 1,1,1,1,1,1,1,1,1,8,36,120,330,792,1716,3432,48477,368797,2002429,
%T 8685469,31964725,103593205,303129685,6156709438,66139517554,
%U 498859498016,2961422519550,14715247475500,63593705003400,245316996896400,6498850067259615
%N Number of 7 up, 7 down permutations of [n].
%H Alois P. Heinz, <a href="/A229888/b229888.txt">Table of n, a(n) for n = 0..200</a>
%e a(8) = 1: 12345678.
%e a(9) = 8: 123456798, 123456897, 123457896, 123467895, 123567894, 124567893, 134567892, 234567891.
%p b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(`if`(t=7,
%p b(o-j, u+j-1, 1), b(u+j-1, o-j, t+1)), j=1..o))
%p end:
%p a:= n-> b(0, n, 0):
%p seq(a(n), n=0..35);
%Y Column k=7 of A229892.
%K nonn,eigen
%O 0,10
%A _Alois P. Heinz_, Oct 02 2013