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A379283
G.f. A(x) satisfies A(x) = 1/( (1 - x*A(x)^3) * (1 - x*A(x)) )^2.
3
1, 4, 42, 612, 10387, 192312, 3766316, 76716624, 1608691229, 34495221722, 752911467734, 16671973428486, 373609441084507, 8457057155407906, 193087102810266948, 4441320670474030222, 102821800799622552713, 2394063264658388861914, 56025225620739219372819
OFFSET
0,2
FORMULA
G.f.: B(x)^2 where B(x) is the g.f. of A379287.
a(n) = 2 * Sum_{k=0..n} binomial(2*n+5*k+2,k) * binomial(3*n+3*k+1,n-k)/(2*n+5*k+2).
PROG
(PARI) a(n) = 2*sum(k=0, n, binomial(2*n+5*k+2, k)*binomial(3*n+3*k+1, n-k)/(2*n+5*k+2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Dec 19 2024
STATUS
approved