The Gauss factorial n_5!.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =24a(6) =144a(7) =1008a(8) =8064a(9) =72576a(10) =72576a(11) =798336a(12) =9580032a(13) =124540416a(14) =1743565824a(15) =1743565824a(16) =27897053184a(17) =474249904128