OFFSET
3,2
FORMULA
E.g.f.: (1/sqrt(1-x^2))*((x/(1-x))^3)/3!.
a(n) = (n!/3!) * Sum_{k=0..floor((n-3)/2)} binomial(2*k, k)*binomial(n-2*k-1, 2)/(4^k), n >= 3.
PROG
(PARI) a(n) = {my(p = polhermite(n)^2/2^n); my(q = sum(k=1, poldegree(p), polcoef(p, k)/2^(k/2)*x^k)); abs(polcoef(q, 6)); } \\ Michel Marcus, Jan 06 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Aug 23 2005
STATUS
approved