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Number of connected triangle-free graphs on n unlabeled nodes.
17

%I #38 Nov 19 2021 17:41:05

%S 1,1,1,3,6,19,59,267,1380,9832,90842,1144061,19425052,445781050,

%T 13743625184,566756900370,31125101479652

%N Number of connected triangle-free graphs on n unlabeled nodes.

%H P. J. Cameron, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/groups.html">Sequences realized by oligomorphic permutation groups</a>, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

%H CombOS - Combinatorial Object Server, <a href="http://combos.org/nauty">Generate graphs</a>

%H Satvik Singh, <a href="https://arxiv.org/abs/2010.11891">Can entanglement hide behind triangle-free graphs?</a>, arXiv:2010.11891 [quant-ph], 2020.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ConnectedGraph.html">Connected Graph</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Triangle-FreeGraph.html">Triangle-Free Graph</a>

%Y Inverse Euler transform of A006785.

%Y Table of graphs on n nodes with clique number k is A126744.

%Y Column k=1 of A283417.

%K hard,more,nonn,nice

%O 1,4

%A _Peter J. Cameron_

%E 2 more terms from _Vladeta Jovovic_, May 17 2008

%E 2 more terms from A006785 by _Martin Fuller_, May 01 2015