A349367 - OEIS

A349367

Number of n-element unlabeled disconnected N-free posets.

0, 1, 2, 6, 18, 65, 241, 984, 4250, 19590, 95484, 491459, 2660030, 15100494, 89648378

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OFFSET

1,3

LINKS

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

Salah Uddin Mohammad, Md. Shah Noor, and Md. Rashed Talukder, An Exact Enumeration of the Unlabeled Disconnected Posets, J. Int. Seq., Vol. 25 (2022), Article 22.5.4.

Salah Uddin Mohammad, Md. Shah Noor, and Md. Rashed Talukder, Recognition of N-free Posets by Using the Poset Matrix, Asia Pac. J. Math., Vol. 11 (2024), Article no. 72.

FORMULA

a(n) = A202182(n) - A202180(n).

CROSSREFS

KEYWORD

nonn,more

AUTHOR

STATUS

approved