The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A202181 Triangle read by rows: T(n,k) = number of n-element unlabeled N-free posets of height k (1 <= k <= n). 1
 1, 1, 1, 1, 3, 1, 1, 7, 6, 1, 1, 13, 24, 10, 1, 1, 25, 77, 61, 15, 1, 1, 43, 228, 291, 130, 21, 1, 1, 76, 644, 1229, 856, 246, 28, 1, 1, 128, 1776, 4872, 4840, 2136, 427, 36, 1, 1, 216, 4854, 18711, 25107, 15543, 4733, 694, 45, 1, 1, 354, 13184, 70858, 124167, 101538, 43120, 9577, 1071, 55, 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. LINKS EXAMPLE Triangle begins: 1 1 1 1 3 1 1 7 6 1 1 13 24 10 1 1 25 77 61 15 1 1 43 228 291 130 21 1 1 76 644 1229 856 246 28 1 1 128 1776 4872 4840 2136 427 36 1 1 216 4854 18711 25107 15543 4733 694 45 1 1 354 13184 70858 124167 101538 43120 9577 1071 55 1 ... CROSSREFS Row sums give A202182. Cf. A202178, A003430, A007453, A053554. Sequence in context: A287213 A284631 A154341 * A130749 A250118 A250119 Adjacent sequences:  A202178 A202179 A202180 * A202182 A202183 A202184 KEYWORD nonn,tabl AUTHOR N. J. A. Sloane, Dec 13 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 28 01:48 EDT 2020. Contains 334671 sequences. (Running on oeis4.)