A385699 G.f. A(x) satisfies A(x) = 1/( 1 - x*(A(x) + A(-x))*(A(x) + A(w*x) + A(w^2*x))/6 ), where w = exp(2*Pi*i/3).
1, 1, 1, 2, 5, 13, 24, 88, 181, 523, 1616, 4891, 10540, 42009, 94953, 294102, 957259, 3028320, 6864540, 28208447, 66180997, 211105506, 703497178, 2273009790, 5283518340, 22058432677, 52795736539, 171169636087, 578132050147, 1891182035377, 4462525373212
Offset: 0
Keywords
Formula
a(0) = 1; a(n) = Sum_{i, j, k>=0 and i+2*j+3*k=n-1} a(i) * a(2*j) * a(3*k).