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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. 2
1, 1, 4, 12, 47, 174 (list; graph; refs; listen; history; text; internal format)
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..5.

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

EXAMPLE

See Sloane's link.

CROSSREFS

Cf. A000112, A022017.

Sequence in context: A149374 A149375 A035310 * A151441 A032380 A057346

Adjacent sequences:  A022013 A022014 A022015 * A022017 A022018 A022019

KEYWORD

nonn,more

AUTHOR

Franklin T. Adams-Watters, Mar 30 2002

STATUS

approved

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Last modified October 21 20:44 EDT 2019. Contains 328315 sequences. (Running on oeis4.)