Number of permutations p of {1,...,n} satisfying p(1)=1 and, if n>1, |p(i)-p((i mod n)+1)| is in {2,3} for i from 1 to n.

A174469

Number of permutations p of {1,...,n} satisfying p(1)=1 and, if n>1, |p(i)-p((i mod n)+1)| is in {2,3} for i from 1 to n.

Terms

    a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =0a(6) =0a(7) =0a(8) =0a(9) =2a(10) =2a(11) =2a(12) =2a(13) =2a(14) =4a(15) =6a(16) =8a(17) =10a(18) =12a(19) =16a(20) =22a(21) =30a(22) =40a(23) =52a(24) =68a(25) =90a(26) =120a(27) =160a(28) =212a(29) =280

External references