The even bisection of A000594.

Terms

a(0) =-24a(1) =-1472a(2) =-6048a(3) =84480a(4) =-115920a(5) =-370944a(6) =401856a(7) =987136a(8) =2727432a(9) =-7109760a(10) =-12830688a(11) =21288960a(12) =13865712a(13) =24647168a(14) =-29211840a(15) =-196706304a(16) =165742416a(17) =167282496a(18) =-255874080a(19) =408038400a(20) =101267712a(21) =-786948864a(22) =-447438528a(23) =248758272a(24) =611981400a(25) =850430336a(26) =1758697920