OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..250
FORMULA
a(n) = (2n)! * [x^(2n)] exp(x^2/2+x^4/4+x^8/8).
MAPLE
b:= proc(n) option remember; `if`(n<0, 0, `if`(n=0, 1,
add(mul(n-i, i=1..j-1)*b(n-j), j=[2, 4, 8])))
end:
a:= n-> b(2*n):
seq(a(n), n=0..20);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 18 2015
STATUS
approved