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A202180 Number of n-element unlabeled connected N-free posets. 2
1, 1, 3, 9, 31, 115, 474, 2097, 9967, 50315, 268442, 1505463, 8840306, 54169431 (list; graph; refs; listen; history; text; internal format)
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: A049154 A225305 A110136 * A151034 A151035 A151036

Adjacent sequences:  A202177 A202178 A202179 * A202181 A202182 A202183

KEYWORD

nonn,changed

AUTHOR

N. J. A. Sloane, Dec 13 2011

EXTENSIONS

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

STATUS

approved

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Last modified June 5 03:12 EDT 2020. Contains 334828 sequences. (Running on oeis4.)