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A367045
G.f. satisfies A(x) = 1 - x^2 + x*A(x)^4.
1
1, 1, 3, 18, 112, 755, 5348, 39302, 296916, 2291861, 17997052, 143319918, 1154728056, 9395809374, 77099733884, 637298480966, 5301568498768, 44351526986704, 372890978840156, 3149155955471690, 26702387443603200, 227238745573918511, 1940201017862028108
OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*(n-2*k)+1,k) * binomial(4*(n-2*k),n-2*k)/(3*(n-2*k)+1).
PROG
(PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(3*(n-2*k)+1, k)*binomial(4*(n-2*k), n-2*k)/(3*(n-2*k)+1));
CROSSREFS
Cf. A367041.
Sequence in context: A357203 A215047 A376031 * A346578 A213099 A199259
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 03 2023
STATUS
approved