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A193387 Triangle read by rows: T(n,k) (n>=1, 1 <= k <= n) = number of n-element unlabeled interval posets of height k. 2
1, 1, 1, 1, 3, 1, 1, 7, 6, 1, 1, 15, 26, 10, 1, 1, 31, 100, 69, 15, 1, 1, 63, 366, 412, 150, 21, 1, 1, 127, 1317, 2305, 1270, 286, 28, 1, 1, 255, 4743, 12551, 9920, 3236, 497, 36, 1, 1, 511, 17275, 67933, 74525, 33301, 7210, 806, 45, 1, 1, 1023, 64029, 370168, 551232, 325860, 93926, 14540, 1239, 55, 1, 1, 2047, 242371, 2046980, 4072130, 3109628, 1151416, 232891, 27147, 1825, 66, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,5

REFERENCES

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

Soheir Mohamed Khamis, Exact Counting of Unlabeled Rigid Interval Posets Regarding or Disregarding Height, Order (journal), published on-line, 2011; DOI: 10.1007/s11083-011-9213-5.

LINKS

Table of n, a(n) for n=1..78.

EXAMPLE

Triangle begins

1

1 1

1 3 1

1 7 6 1

1 15 26 10 1

1 31 100 69 15 1

1 63 366 412 150 21 1

1 127 1317 2305 1270 286 28 1

1 255 4743 12551 9920 3236 497 36 1

1 511 17275 67933 74525 33301 7210 806 45 1

...

CROSSREFS

Row sums give A022493. Cf. A193357.

Sequence in context: A080417 A008277 A218577 * A185982 A263858 A263862

Adjacent sequences:  A193384 A193385 A193386 * A193388 A193389 A193390

KEYWORD

nonn,tabl

AUTHOR

N. J. A. Sloane, Aug 26 2011

STATUS

approved

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Last modified November 13 19:25 EST 2018. Contains 317149 sequences. (Running on oeis4.)