The number of permutations p of {1,...,n} satisfying |p(i)-p(i+1)| is in {4,5} for i from 1 to n-1.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =2a(8) =18a(9) =12a(10) =0a(11) =0a(12) =0a(13) =0a(14) =0a(15) =0a(16) =30a(17) =136a(18) =112a(19) =0a(20) =0a(21) =0a(22) =0a(23) =0a(24) =0a(25) =400a(26) =1348a(27) =1352a(28) =408a(29) =180