A202179 - OEIS

A202179

Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (2 <= k <= n).

%I #11 Jun 08 2020 05:24:10

%S 1,2,1,3,5,1,4,17,9,1,5,45,50,14,1,6,115,218,114,20,1,7,278,851,709,

%T 224,27,1,8,679,3161,3818,1867,398,35,1,9,1666,11507,19042,13113,4276,

%U 657,44,1,10,4167,41837,91383,83222,37898,8845,1025,54,1

%N Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (2 <= k <= n).

%H 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 Triangle begins: 1

%e 2 1

%e 3 5 1

%e 4 17 9 1

%e 5 45 50 14 1

%e 6 115 218 114 20 1

%e 7 278 851 709 224 27 1

%e 8 679 3161 3818 1867 398 35 1

%e 9 1666 11507 19042 13113 4276 657 44 1

%e 10 4167 41837 91383 83222 37898 8845 1025 54 1

%e ...

%Y See A202178 for another version. Row sums give A202180.

%K nonn,tabl

%O 2,2

%A _N. J. A. Sloane_, Dec 13 2011