cp's OEIS Frontend

A202181 Triangle read by rows: T(n,k) = number of n-element unlabeled N-free posets of height k (1 <= k <= n).

%I A202181 #13 Jun 08 2020 05:24:27
%S A202181 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,
%T A202181 1,1,76,644,1229,856,246,28,1,1,128,1776,4872,4840,2136,427,36,1,1,
%U A202181 216,4854,18711,25107,15543,4733,694,45,1,1,354,13184,70858,124167,101538,43120,9577,1071,55,1
%N A202181 Triangle read by rows: T(n,k) = number of n-element unlabeled N-free posets of height k (1 <= k <= n).
%H A202181 Soheir M. Khamis, <a href="https://doi.org/10.1016/S0012-365X(03)00106-7">Height counting of unlabeled interval and N-free posets</a>, Discrete Math. 275 (2004), no. 1-3, 165-175.
%e A202181 Triangle begins:
%e A202181 1
%e A202181 1 1
%e A202181 1 3 1
%e A202181 1 7 6 1
%e A202181 1 13 24 10 1
%e A202181 1 25 77 61 15 1
%e A202181 1 43 228 291 130 21 1
%e A202181 1 76 644 1229 856 246 28 1
%e A202181 1 128 1776 4872 4840 2136 427 36 1
%e A202181 1 216 4854 18711 25107 15543 4733 694 45 1
%e A202181 1 354 13184 70858 124167 101538 43120 9577 1071 55 1
%e A202181 ...
%Y A202181 Row sums give A202182. Cf. A202178, A003430, A007453, A053554.
%K A202181 nonn,tabl
%O A202181 1,5
%A A202181 _N. J. A. Sloane_, Dec 13 2011