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A364596
G.f. satisfies A(x) = 1/(1-x) + x^3*(1-x)*A(x)^4.
4
1, 1, 1, 2, 4, 7, 15, 36, 82, 191, 471, 1166, 2884, 7267, 18523, 47349, 121821, 315781, 822165, 2148811, 5641035, 14864295, 39287907, 104154066, 276899112, 737984583, 1971375679, 5277570860, 14156881590, 38045460023, 102421374775, 276174537027, 745822179831
OFFSET
0,4
FORMULA
a(n) = Sum_{k=0..floor(n/3)} binomial(n-k,2*k) * binomial(4*k,k) / (3*k+1).
PROG
(PARI) a(n) = sum(k=0, n\3, binomial(n-k, 2*k)*binomial(4*k, k)/(3*k+1));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jul 29 2023
STATUS
approved