G.f. C(x) satisfies: C(x) = (1 - x*C(x))*(1 - 2*x*C(x)) / (1 - 3*x*C(x))^2.

A341963

G.f. C(x) satisfies: C(x) = (1 - x*C(x))*(1 - 2*x*C(x)) / (1 - 3*x*C(x))^2.

Terms

    a(0) =1a(1) =3a(2) =20a(3) =165a(4) =1520a(5) =14982a(6) =154588a(7) =1648713a(8) =18029456a(9) =201063402a(10) =2277890472a(11) =26143479954a(12) =303322798896

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