a(n)=2*n!/d(n!); d(m)=A000005(m) is the number of divisors of m.

A125721

a(n)=2*n!/d(n!); d(m)=A000005(m) is the number of divisors of m.

Terms

    a(0) =2a(1) =2a(2) =2a(3) =3a(4) =6a(5) =15a(6) =48a(7) =168a(8) =840a(9) =4536a(10) =26880a(11) =147840a(12) =1209600a(13) =7862400a(14) =67267200a(15) =648648000a(16) =7783776000a(17) =66162096000a(18) =871782912000

External references