a(n) = Product_{i=4..n} (prime(i) - 6).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =35a(6) =385a(7) =5005a(8) =85085a(9) =1956955a(10) =48923875a(11) =1516640125a(12) =53082404375