a(n) = denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =60a(5) =5a(6) =80a(7) =720a(8) =7920a(9) =55440a(10) =55440a(11) =6160a(12) =6160a(13) =18480a(14) =425040a(15) =5525520a(16) =160240080a(17) =160240080a(18) =53413360a(19) =53413360a(20) =480720240a(21) =480720240a(22) =19709529840a(23) =19709529840a(24) =39419059680a(25) =197095298400