Upper central divisor of n-th primorial.

Terms

a(0) =2a(1) =3a(2) =6a(3) =15a(4) =55a(5) =182a(6) =715a(7) =3135a(8) =15015a(9) =81345a(10) =448630a(11) =2733549a(12) =17490603a(13) =114388729a(14) =785147363a(15) =5708795638a(16) =43850489690a(17) =342503171205