Triangle T(n,k), n>=3, 3<=k<=n, read by rows. Number of ways to make n selections without replacement from a circular array of n unlabeled cells (ignoring rotations and reflection), such that the first selection of a cell adjacent to previously selected cells occurs on the k-th selection.

A249796

Triangle T(n,k), n>=3, 3<=k<=n, read by rows. Number of ways to make n selections without replacement from a circular array of n unlabeled cells (ignoring rotations and reflection), such that the first selection of a cell adjacent to previously selected cells occurs on the k-th selection.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =2a(4) =6a(5) =4a(6) =6a(7) =18a(8) =28a(9) =8a(10) =24a(11) =72a(12) =128a(13) =120a(14) =16a(15) =120a(16) =360a(17) =672a(18) =840a(19) =496a(20) =32a(21) =720a(22) =2160a(23) =4128a(24) =5760a(25) =5312a(26) =2016a(27) =64a(28) =5040a(29) =15120

External references