A349401 Number of unlabeled disconnected posets with n elements.

0, 0, 1, 2, 6, 19, 80, 395, 2487, 19890, 206565, 2804453, 49872647, 1158843214, 35049606566, 1374685228988, 69690886873398, 4554367168841547

Offset

0,4

Links

Table of n, a(n) for n=0..17.

Gunnar Brinkmann and Brendan D. McKay, Posets on up to 16 points.

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.

Formula

a(n) = A000112(n) - A000608(n).

Crossrefs

Cf. A000112, A000608, A342500.

Sequence in context: A079564 A273988 A287897 * A344317 A266933 A291106

Adjacent sequences: A349398 A349399 A349400 * A349402 A349403 A349404

Keyword

nonn,more

Author

Salah Uddin Mohammad, Nov 15 2021

Status

approved