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A202179 Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (2 <= k <= n). 2
1, 2, 1, 3, 5, 1, 4, 17, 9, 1, 5, 45, 50, 14, 1, 6, 115, 218, 114, 20, 1, 7, 278, 851, 709, 224, 27, 1, 8, 679, 3161, 3818, 1867, 398, 35, 1, 9, 1666, 11507, 19042, 13113, 4276, 657, 44, 1, 10, 4167, 41837, 91383, 83222, 37898, 8845, 1025, 54, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

2,2

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=2..56.

EXAMPLE

Triangle begins: 1

2 1

3 5 1

4 17 9 1

5 45 50 14 1

6 115 218 114 20 1

7 278 851 709 224 27 1

8 679 3161 3818 1867 398 35 1

9 1666 11507 19042 13113 4276 657 44 1

10 4167 41837 91383 83222 37898 8845 1025 54 1

...

CROSSREFS

See A202178 for another version. Row sums give A202180.

Sequence in context: A110197 A124819 A124019 * A297519 A297749 A173588

Adjacent sequences:  A202176 A202177 A202178 * A202180 A202181 A202182

KEYWORD

nonn,tabl

AUTHOR

N. J. A. Sloane, Dec 13 2011

STATUS

approved

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Last modified June 1 04:57 EDT 2020. Contains 334758 sequences. (Running on oeis4.)