a(n) = lcm{prime(i)-1, i=1..n}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =12a(5) =60a(6) =60a(7) =240a(8) =720a(9) =7920a(10) =55440a(11) =55440a(12) =55440a(13) =55440a(14) =55440a(15) =1275120a(16) =16576560a(17) =480720240a(18) =480720240a(19) =480720240a(20) =480720240a(21) =480720240a(22) =480720240a(23) =19709529840a(24) =19709529840a(25) =39419059680a(26) =197095298400