OFFSET
5,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 5..500
EXAMPLE
a(5) = 1: 12345.
a(6) = 17: 124365, 124635, 124653, 125346, 132456, 134256, 134526, 134562, 213456, 231456, 234156, 234516, 234561, 312456, 412356, 512346, 612345.
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^(o-j), x, 7), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 6):
seq(a(n), n=5..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 14 2015
STATUS
approved