Number of permutations p of [n] such that p(i) > p(i+1) iff i == 0 (mod 8).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =8a(10) =44a(11) =164a(12) =494a(13) =1286a(14) =3002a(15) =6434a(16) =12869a(17) =194464a(18) =1925200a(19) =12394480a(20) =62224336a(21) =261667792a(22) =959874928a(23) =3154435120a(24) =9464040829a(25) =210311057024