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Number of permutations p of [n] such that the up-down signature of 0,p has nonnegative partial sums with a maximal value of nine.
2

%I #5 Jul 01 2018 18:05:51

%S 1,9,2071,20845,1553153,17662969,908651571,11670560732,512693233164,

%T 7392808621010,303061463720474,4869546964922509,194661534866479194,

%U 3459210686800253224,138131753631241199208,2695708505172764233290,109038227244360661170616

%N Number of permutations p of [n] such that the up-down signature of 0,p has nonnegative partial sums with a maximal value of nine.

%H Alois P. Heinz, <a href="/A316396/b316396.txt">Table of n, a(n) for n = 9..451</a>

%F a(n) = A262171(n) - A262170(n).

%p b:= proc(u, o, c, k) option remember;

%p `if`(c<0 or c>k, 0, `if`(u+o=0, 1,

%p add(b(u-j, o-1+j, c+1, k), j=1..u)+

%p add(b(u+j-1, o-j, c-1, k), j=1..o)))

%p end:

%p a:= n-> b(n, 0$2, 9)-b(n, 0$2, 8):

%p seq(a(n), n=9..25);

%Y Column k=9 of A258829.

%Y Cf. A262170, A262171.

%K nonn

%O 9,2

%A _Alois P. Heinz_, Jul 01 2018