A379331 G.f. A(x) satisfies A(x) = 1/sqrt( (1 - 2*x*A(x)^3) * (1 - 2*x*A(x)) ).
1, 2, 12, 100, 976, 10432, 118216, 1395200, 16965664, 211078656, 2674095616, 34378044416, 447359023072, 5881178595328, 77992591652992, 1042089880305664, 14015275654390272, 189583355671740416, 2577607282441795840, 35205701425533550592, 482822120552883164160
Offset: 0
Keywords
Programs
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PARI
a(n) = 2^n*sum(k=0, n, binomial(n/2+2*k+1/2, k)*binomial(3*n/2-1/2, n-k)/(n+4*k+1));
Formula
a(n) = 2^n * Sum_{k=0..n} binomial(n/2+2*k+1/2,k) * binomial(3*n/2-1/2,n-k)/(n+4*k+1).