A361912 The number of unlabeled graded posets with n elements.

1, 1, 2, 4, 10, 28, 93, 354, 1621, 9110, 64801, 595976, 7204091, 115561423, 2473540433, 70853213144, 2720354016419, 140170631441858, 9702605436760235, 903309202327818566, 113234129823368903523, 19137461395401601912043, 4366007821745938984134203

Offset: 0

Author

Martin Rubey, Mar 29 2023

Keywords

• nonn

Comments

A partially ordered set is graded if all maximal chains have the same length. This is called tiered by some authors.

Links

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

Crossrefs

Row sums of A361957.

Cf. A000112, A223911 (labeled), A001833, A361920, A361959 (connected).

Programs

PARI

\\ See PARI link in A361957 for program code.
A361912seq(20) \\ Andrew Howroyd, Apr 03 2023

Sage

sum(1 for P in posets(n) if P.is_graded())

Extensions

Terms a(8) and beyond from Andrew Howroyd, Mar 30 2023