A022017 Number of connected partially ordered sets with n "lines": pairs (a,b) where a < b and there is no c with a < c < b. The lines form the minimal basis for the partial ordering.

1, 3, 8, 29, 103, 442, 1953, 9502, 48533, 262634, 1485764, 8777397, 53869119

Offset: 1

Author

Franklin T. Adams-Watters, Mar 30 2002

Keywords

• nonn
• hard
• more

Comments

The points are unlabeled.

Examples

			See Sloane's link.
		

References

• See A000112 for references and links about partially ordered sets.

Links

• N. J. A. Sloane, Illustration of initial terms of A022016 and A022017.
• Index entries for sequences related to posets

Crossrefs

Cf. A000112, A000608, A022016. Column sums of A342590.

Extensions

a(6)-a(9) from A342590. - R. J. Mathar, Mar 21 2021

a(10)-a(13) from Rico Zöllner and Konrad Handrich, Nov 19 2024