a(1) = 1; a(n)= 2*lcm(n, a(n - 1)).

Terms

a(0) =1a(1) =4a(2) =24a(3) =48a(4) =480a(5) =960a(6) =13440a(7) =26880a(8) =161280a(9) =322560a(10) =7096320a(11) =14192640a(12) =369008640a(13) =738017280a(14) =1476034560a(15) =2952069120a(16) =100370350080a(17) =200740700160