Restricted permutations.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =4a(5) =16a(6) =80a(7) =672a(8) =4896a(9) =49920a(10) =460032a(11) =5598720a(12) =62584320a(13) =885381120a(14) =11644323840a(15) =187811205120