OFFSET
6,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 6..500
EXAMPLE
a(6) = 22: 245613, 245631, 256341, 345261, 346251, 356124, 356142, 356214, 356412, 356421, 452361, 453612, 453621, 462351, 463512, 463521, 561342, 562314, 562413, 562431, 563241, 564231.
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, 6), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 5):
seq(a(n), n=6..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 14 2015
STATUS
approved