A367072 G.f. satisfies A(x) = 1 + x + 2*x^3*A(x)^3.
1, 1, 0, 2, 6, 6, 14, 60, 120, 216, 732, 2028, 4240, 11280, 33696, 83328, 207072, 591360, 1606752, 4102656, 11172528, 31167280, 83112000, 223249824, 619860960, 1699634784, 4603619616, 12689107200, 35170240512, 96523315200, 265883115264, 738668408064
Offset: 0
Keywords
Programs
-
PARI
a(n) = sum(k=0, n\3, 2^k*binomial(2*k+1, n-3*k)*binomial(3*k, k)/(2*k+1));
Formula
a(n) = Sum_{k=0..floor(n/3)} 2^k * binomial(2*k+1,n-3*k) * A001764(k).