a(n) = 2^(n*(n-1)/2)*Product_{j=0..n-1} (4*j+2)!/(n+2*j+1)!.

A341275

a(n) = 2^(n*(n-1)/2)*Product_{j=0..n-1} (4*j+2)!/(n+2*j+1)!.

Terms

    a(0) =1a(1) =4a(2) =60a(3) =3328a(4) =678912a(5) =508035072

External references