OFFSET
6,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 6..659
MAPLE
b:= (n, k)-> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(n-j)*(k-1)^j, j=0..n-1)):
a:= n-> (k-> add((-1)^i*b(n, k-i)/(i!*(k-i)!), i=0..k))(6):
seq(a(n), n=6..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 26 2018
STATUS
approved