a(n) = (5*n)!/(4*n+1)!.A365341a(n) = (5*n)!/(4*n+1)!.Terms a(0) =1a(1) =1a(2) =10a(3) =210a(4) =6840a(5) =303600a(6) =17100720a(7) =1168675200a(8) =93963542400External referencesoeis: A365341