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A366499
G.f. A(x) satisfies A(x) = 1 + x / ((1+x)^3*A(x)^2).
6
1, 1, -5, 25, -145, 945, -6641, 49057, -375361, 2948353, -23634049, 192554753, -1589812225, 13272519937, -111850866433, 950220134913, -8129133081601, 69971682467841, -605546841831425, 5265763716550657, -45988028107350017, 403192288488677377
OFFSET
0,3
FORMULA
G.f.: A(x) = 1/B(-x) where B(x) is the g.f. of A213282.
a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(n+2*k-1,n-k) * binomial(3*k-1,k) / (3*k-1).
PROG
(PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(n+2*k-1, n-k)*binomial(3*k-1, k)/(3*k-1));
KEYWORD
sign
AUTHOR
Seiichi Manyama, Oct 11 2023
STATUS
approved