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

0,3

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

Prog

(Sage) sum(1 for P in posets(n) if P.is_graded())
(PARI) \\ See PARI link in A361957 for program code.
A361912seq(20) \\ Andrew Howroyd, Apr 03 2023

Crossrefs

Row sums of A361957.

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

Sequence in context: A271207 A091175 A090594 * A188496 A369079 A191501

Adjacent sequences: A361909 A361910 A361911 * A361913 A361914 A361915

Keyword

nonn

Author

Martin Rubey, Mar 29 2023

Extensions

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

Status

approved