a(n) = (2/3)*(2*n+1)*(2*n-1)!*binomial(3*n,2*n).
A081321
a(n) = (2/3)*(2*n+1)*(2*n-1)!*binomial(3*n,2*n).
Terms
- a(0) =6a(1) =300a(2) =47040a(3) =14968800a(4) =7991343360
External references
- oeis: A081321
A081321
a(n) = (2/3)*(2*n+1)*(2*n-1)!*binomial(3*n,2*n).