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

Offset

1,3

Links

Table of n, a(n) for n=1..15.

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.

Formula

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

Crossrefs

Cf. A202182, A202180.

Sequence in context: A150072 A150073 A150074 * A300335 A108066 A052863

Adjacent sequences: A349364 A349365 A349366 * A349368 A349369 A349370

Keyword

nonn,more

Author

Salah Uddin Mohammad, Nov 15 2021

Status

approved