OFFSET
5,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 5..500
EXAMPLE
a(5) = 10: 23451, 24513, 24531, 34251, 35241, 45123, 45132, 45213, 45312, 45321.
MAPLE
b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
b(u-j, o+j-1), j=1..u) +add(convert(series(
b(u+j-1, o-j)*x^u, x, 4), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 3):
seq(a(n), n=5..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 14 2015
STATUS
approved