A022016 Number of partially ordered sets with no isolated points and 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, 1, 4, 12, 47, 174, 749, 3291, 15675, 78104, 411042

Offset

0,3

Comments

The points are unlabeled.

References

See A000112 for references and links about partially ordered sets.

Links

Table of n, a(n) for n=0..10.

N. J. A. Sloane, Illustration of initial terms of A022016 and A022017.

Example

See Sloane's link.

Crossrefs

Cf. A000112, A022017, A342447.

Sequence in context: A149374 A149375 A035310 * A151441 A361428 A032380

Adjacent sequences: A022013 A022014 A022015 * A022017 A022018 A022019

Keyword

nonn,more,changed

Author

Franklin T. Adams-Watters, Mar 30 2002

Extensions

a(6)-a(10) from Rico Zöllner and Konrad Handrich, Oct 08 2024

Status

approved