a(n) = n * C(2*3^(n-1), n) for n>=1.A136636a(n) = n * C(2*3^(n-1), n) for n>=1.Terms a(0) =2a(1) =30a(2) =2448a(3) =1265004a(4) =4368213360External referencesoeis: A136636