A193357 Triangle read by rows: T(n,k) (n>=1, 1 <= k <= n) = number of n-element unlabeled rigid interval posets of height k.

1, 0, 1, 0, 1, 1, 0, 1, 3, 1, 0, 1, 8, 6, 1, 0, 1, 20, 29, 10, 1, 0, 1, 51, 128, 75, 15, 1, 0, 1, 134, 555, 500, 160, 21, 1, 0, 1, 367, 2427, 3190, 1480, 301, 28, 1, 0, 1, 1048, 10864, 20129, 12835, 3661, 518, 36, 1, 0, 1, 3119, 50145, 127912, 108308, 41041, 7980, 834, 45, 1, 0, 1, 9655, 239581, 827053, 907923, 441553, 111671, 15828, 1275, 55, 1

Offset

1,9

Links

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

Soheir Mohamed Khamis, Exact Counting of Unlabeled Rigid Interval Posets Regarding or Disregarding Height, Order 29, pp. 443-461 (2012).

Example

Triangle begins
1
0 1
0 1 1
0 1 3 1
0 1 8 6 1
0 1 20 29 10 1
0 1 51 128 75 15 1
0 1 134 555 500 160 21 1
0 1 367 2427 3190 1480 301 28 1
0 1 1048 10864 20129 12835 3661 518 36 1
0 1 3119 50145 127912 108308 41041 7980 834 45 1
0 1 9655 239581 827053 907923 441553 111671 15828 1275 55 1
0 1 31024 1186941 5474614 7654921 4664814 1482110 26944 29175 1870 66 1
...

Crossrefs

Row sums = A138265. Cf. A193387.

Sequence in context: A257050 A274494 A274490 * A361953 A112413 A294219

Adjacent sequences: A193354 A193355 A193356 * A193358 A193359 A193360

Keyword

nonn,tabl

Author

N. J. A. Sloane, Aug 26 2011

Status

approved