a(p^n)=p^(n+1)(p-1) if p is prime and a(nm)=lcm(a(n),a(m)) if gcd(n,m)=1.

Terms

a(0) =1a(1) =4a(2) =18a(3) =8a(4) =100a(5) =36a(6) =294a(7) =16a(8) =54a(9) =100a(10) =1210a(11) =72a(12) =2028a(13) =588a(14) =900a(15) =32a(16) =4624a(17) =108a(18) =6498a(19) =200a(20) =882a(21) =2420a(22) =11638a(23) =144a(24) =500a(25) =2028a(26) =162a(27) =1176a(28) =23548a(29) =900