A193387 Triangle read by rows: T(n,k) (n>=1, 1 <= k <= n) = number of n-element unlabeled interval posets of height k.

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

Offset

1,5

Links

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

Soheir M. Khamis, 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 29, pp. 443-461 (2012).

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