Number of permutations s of {1,2,...,n} such that |s(i)-i| for i=1,2,...,n are all distinct.

Terms

a(0) =1a(1) =1a(2) =0a(3) =0a(4) =4a(5) =4a(6) =0a(7) =0a(8) =32a(9) =96a(10) =0a(11) =0a(12) =992a(13) =2512a(14) =0a(15) =0a(16) =50512a(17) =144144a(18) =0a(19) =0a(20) =3717888a(21) =11068560a(22) =0a(23) =0a(24) =378849504a(25) =1269763552a(26) =0a(27) =0a(28) =51487458416a(29) =181839037824