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A372137
G.f. A(x) satisfies A(x) = 1/( 1 - x * (1 + 9*x)^(1/3) * A(x)^2 ).
2
1, 1, 6, 21, 181, 771, 7728, 34689, 385632, 1732971, 21041598, 92147697, 1217109951, 5099210686, 73380609681, 289623783084, 4564472639880, 16722146775195, 290985244619874, 974044248064611, 18925364858562927, 56848541164586820, 1251693011560795635
OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} 9^(n-k) * binomial(3*k,k) * binomial(k/3,n-k)/(2*k+1).
PROG
(PARI) a(n) = sum(k=0, n, 9^(n-k)*binomial(3*k, k)*binomial(k/3, n-k)/(2*k+1));
CROSSREFS
Cf. A372124.
Sequence in context: A210443 A179768 A131960 * A244299 A143049 A213680
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 20 2024
STATUS
approved