A202179 -id:A202179 - cp's OEIS frontend

A202180 Number of n-element unlabeled connected N-free posets.

Original entry on oeis.org

1, 1, 3, 9, 31, 115, 474, 2097, 9967, 50315, 268442, 1505463, 8840306, 54169431

Offset: 1

N. J. A. Sloane, Dec 13 2011

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

Row sums of A202178 and A202179.

Cf. A003430, A007453, A053554.

Missing term a(12) inserted by Salah Uddin Mohammad, May 26 2020

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

Original entry on oeis.org

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

N. J. A. Sloane, Dec 13 2011

			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
...

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

See A202179 for another version. Row sums give A202180.

cp's OEIS Frontend

A202180 Number of n-element unlabeled connected N-free posets.

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