login
A366697
G.f. satisfies A(x) = (1 + x)^3 + x*A(x)^3.
1
1, 4, 15, 94, 706, 5769, 49923, 449376, 4164228, 39459852, 380594767, 3724049805, 36876008673, 368835076813, 3720863181033, 37815675159285, 386818379566749, 3979362306753315, 41144521893563511, 427335033811660713, 4456402044181677264
OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} binomial(3*(2*k+1),n-k) * binomial(3*k,k)/(2*k+1).
PROG
(PARI) a(n) = sum(k=0, n, binomial(3*(2*k+1), n-k)*binomial(3*k, k)/(2*k+1));
CROSSREFS
Cf. A364623.
Sequence in context: A332533 A013193 A040025 * A208991 A109365 A352415
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 16 2023
STATUS
approved