a(n) is the denominator of Product_{i=0..n-1} (n-i)^((-1)^ceiling(i/2)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =5a(6) =5a(7) =63a(8) =56a(9) =4a(10) =225a(11) =77a(12) =1232a(13) =312a(14) =65a(15) =2695a(16) =1408a(17) =14144a(18) =9945a(19) =92169a(20) =53504a(21) =28288a(22) =41769a(23) =370139a(24) =447488a(25) =217600a(26) =502775a(27) =1427679a(28) =2684928a(29) =2524160