A379194 G.f. A(x) satisfies A(x) = (1 + x*A(x))^2/(1 - x*A(x)^3).
1, 3, 19, 174, 1883, 22323, 280409, 3666736, 49386326, 680431419, 9544684113, 135852904486, 1957119390279, 28482417043498, 418119577938769, 6184065626127498, 92062362629472668, 1378427894172778961, 20744229318047760620, 313606289763390553200, 4760422971894347226659
Offset: 0
Keywords
Programs
-
PARI
a(n) = sum(k=0, n, binomial(n+3*k+1, k)*binomial(2*n+4*k+2, n-k)/(n+3*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(n+3*k+1,k) * binomial(2*n+4*k+2,n-k)/(n+3*k+1).