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A350783

Triangle read by rows: T(n,k) is the number of n-element unlabeled N-free posets with k connected components.

1, 1, 1, 3, 1, 1, 9, 4, 1, 1, 31, 12, 4, 1, 1, 115, 46, 13, 4, 1, 1, 474, 173, 49, 13, 4, 1, 1, 2097, 727, 188, 50, 13, 4, 1, 1, 9967, 3195, 795, 191, 50, 13, 4, 1, 1, 50315, 15017, 3502, 810, 192, 50, 13, 4, 1, 1

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,4

LINKS

Table of n, a(n) for n=1..55.

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.

EXAMPLE

Triangle begins:

1, 1;

3, 1, 1;

9, 4, 1, 1;

31, 12, 4, 1, 1;

115, 46, 13, 4, 1, 1;

474, 173, 49, 13, 4, 1, 1;

2097, 727, 188, 50, 13, 4, 1, 1;

9967, 3195, 795, 191, 50, 13, 4, 1, 1;

50315, 15017, 3502, 810, 192, 50, 13, 4, 1, 1;

...

CROSSREFS

Row sums give A202182.

Column 1 is A202180.

Cf. A263864 (all posets), A349488 (disconnected).

Sequence in context: A080510 A378163 A350772 * A124496 A074881 A142992

Adjacent sequences: A350780 A350781 A350782 * A350784 A350785 A350786

KEYWORD

nonn,tabl

AUTHOR

Salah Uddin Mohammad, Jan 16 2022

STATUS

approved

URL: https://oeis.org/A350783

⇱ A350783 - OEIS