A354693 - OEIS

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A354693

Number of unlabeled prime posets with n elements.

1, 0, 0, 1, 4, 28, 234, 2585, 36326, 646405, 14528011, 412212506

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OFFSET

1,5

COMMENTS

A poset P is called prime if it is not decomposable. A poset Q is called decomposable if Q can be obtained as the composition (lexicographic product) of the outer poset Q' and the inner posets Qi, 1 <= i <= r, where |Q'| = r > 1 and at least one of the posets Qi is nonsingleton.

LINKS

Table of n, a(n) for n=1..12.

S. M. Khamis, On numerical counting of prime, UPO, and the general type of posets according to heights, Congressus Numerantium, 146 (2000), 157-171.

S. M. Khamis, Recognition of prime posets and one of its applications, J. Egypt. Math. Soc., 14 (1) (2006), 5-13.

CROSSREFS

Cf. A000112, A003430, A202182.

Sequence in context: A030444 A093877 A151830 * A112113 A368967 A369510

Adjacent sequences: A354690 A354691 A354692 * A354694 A354695 A354696

KEYWORD

nonn,more

AUTHOR

Salah Uddin Mohammad, Jun 03 2022

STATUS

approved