OFFSET
0,3
FORMULA
G.f.: A(x) = 1/B(-x) where B(x) is the g.f. of A213336.
a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(n+3*k-1,n-k) * binomial(4*k-1,k) / (4*k-1).
PROG
(PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(n+3*k-1, n-k)*binomial(4*k-1, k)/(4*k-1));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Oct 11 2023
STATUS
approved