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

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

Offset

1,3

Links

Table of n, a(n) for n=1..14.

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

Crossrefs

Row sums of A202178 and A202179.

Cf. A003430, A007453, A053554.

Sequence in context: A225305 A365113 A110136 * A151034 A151035 A151036

Adjacent sequences: A202177 A202178 A202179 * A202181 A202182 A202183

Keyword

nonn,more

Author

N. J. A. Sloane, Dec 13 2011

Extensions

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

Status

approved