A361955 Number of unlabeled connected weakly graded (ranked) posets with n elements.

1, 1, 1, 3, 10, 42, 202, 1146, 7493, 56996, 508609, 5414635, 70214227, 1134439731, 23331152887, 621768153861, 21761221300058, 1009759125475973, 62534859409597022, 5193886959561972984, 580677490292990902682, 87649885799470898359728, 17907726747155924589913398

Offset: 0

Author

Andrew Howroyd, Mar 31 2023

Keywords

• nonn

Comments

Here weakly graded means that there exists a rank function rk from the poset to the integers such that whenever v covers w in the poset, we have rk(v) = rk(w) + 1.

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..40
• Wikipedia, Graded poset.

Crossrefs

Row sums of A361954.

Cf. A000608, A361920, A361953.

Programs

PARI

\\ See PARI link in A361953 for program code.
A361955seq(20)

Formula

Inverse Euler transform of A361920.