1/12 the number of (n+1) X 2 0..5 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction.

A183721

1/12 the number of (n+1) X 2 0..5 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction.

Terms

    a(0) =0a(1) =1a(2) =12a(3) =87a(4) =537a(5) =3070a(6) =16731a(7) =88331a(8) =455804a(9) =2311983a(10) =11571209a(11) =57295330a(12) =281223411a(13) =1370286715a(14) =6635743136a(15) =31964799247a(16) =153273890393a(17) =732031932806

External references