A202178 Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (1 <= k <= n).

1, 0, 1, 0, 2, 1, 0, 3, 5, 1, 0, 4, 17, 9, 1, 0, 5, 45, 50, 14, 1, 0, 6, 115, 218, 114, 20, 1, 0, 7, 278, 851, 709, 224, 27, 1, 0, 8, 679, 3161, 3818, 1867, 398, 35, 1, 0, 9, 1666, 11507, 19042, 13113, 4276, 657, 44, 1, 0, 10, 4167, 41837, 91383, 83222, 37898, 8845, 1025, 54, 1

Offset

1,5

Links

Table of n, a(n) for n=1..66.

Soheir M. Khamis, Height counting of unlabeled interval and N-free posets, Discrete Math. 275 (2004), no. 1-3, 165-175.

Example

Triangle begins:
1
0 1
0 2 1
0 3 5 1
0 4 17 9 1
0 5 45 50 14 1
0 6 115 218 114 20 1
0 7 278 851 709 224 27 1
0 8 679 3161 3818 1867 398 35 1
0 9 1666 11507 19042 13113 4276 657 44 1
0 10 4167 41837 91383 83222 37898 8845 1025 54 1
...

Crossrefs

See A202179 for another version. Row sums give A202180.

Sequence in context: A222211 A145460 A292978 * A035543 A350548 A105546

Adjacent sequences: A202175 A202176 A202177 * A202179 A202180 A202181

Keyword

nonn,tabl

Author

N. J. A. Sloane, Dec 13 2011

Status

approved