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A364478
G.f. satisfies A(x) = 1 + x*A(x)^3 + x^2*A(x)^8.
3
1, 1, 4, 23, 154, 1124, 8675, 69626, 575243, 4859778, 41789764, 364565277, 3218581695, 28702642553, 258172627259, 2339496034381, 21337716782873, 195726876816623, 1804472496834650, 16711389876481027, 155395461519245354, 1450298253483719944
OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..floor(n/2)} binomial(3*n+2*k,k) * binomial(3*n+k,n-2*k) / (2*n+3*k+1).
PROG
(PARI) a(n) = sum(k=0, n\2, binomial(3*n+2*k, k)*binomial(3*n+k, n-2*k)/(2*n+3*k+1));
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 26 2023
STATUS
approved