a(n) = 4^n*(2*n + 1)!/n!.A254619a(n) = 4^n*(2*n + 1)!/n!.Terms a(0) =1a(1) =24a(2) =960a(3) =53760a(4) =3870720a(5) =340623360a(6) =35424829440External referencesoeis: A254619