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A202182 Number of n-element unlabeled N-free posets of height k (1 <= k <= n). 1
1, 2, 5, 15, 49, 180, 715, 3081, 14217, 69905, 363926, 1150036, 69269925 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Khamis, Soheir M., Height counting of unlabeled interval and N-free posets. Discrete Math. 275 (2004), no. 1-3, 165-175.

LINKS

Table of n, a(n) for n=1..13.

CROSSREFS

Row sums of A202181.

From the definition, this sequence should be the same as A003430. I do not understand why they differ - possibly a different definition of "N-free"?

Sequence in context: A000734 A148366 A005751 * A149944 A149945 A149946

Adjacent sequences:  A202179 A202180 A202181 * A202183 A202184 A202185

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 13 2011

STATUS

approved

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Last modified March 31 19:37 EDT 2020. Contains 333151 sequences. (Running on oeis4.)