A374073 Number of connected chainmails with n unlabeled elements.

1, 1, 2, 5, 16, 62, 303, 1842, 14073, 134802

Offset

1,3

Comments

In a poset, a mail is a nonempty set of elements of the poset having a common lower bound. A chainmail is a poset in which every mail has a join. A chainmail is connected if it's connected as a poset.

Links

Table of n, a(n) for n=1..10.

J. F. Du Plessis, Z. Janelidze, and B. A. Wessels, A Primer on Chainmails: Structures for Point-free Connectivity, arXiv:2406.16923 [math.GM], 2024.

Crossrefs

Sequence in context: A210667 A144188 A157314 * A159603 A058117 A007124

Adjacent sequences: A374070 A374071 A374072 * A374074 A374075 A374076

Keyword

nonn,hard,more

Author

Jean F. du Plessis, Jun 27 2024

Status

approved