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Number of 2-connected unlabeled simple graphs with no triangles.
1

%I #9 Jan 15 2023 01:45:13

%S 1,2,6,16,78,415,3374,35860,524386,10193061,263036202,8948113645,

%T 400280198048

%N Number of 2-connected unlabeled simple graphs with no triangles.

%e For n=4 the only example is a 4-cycle.

%Y Cf. A002218 all 2-connected graphs.

%Y Cf. A024607 all connected triangle-free graphs.

%K nonn,hard,more

%O 4,2

%A _Brendan McKay_, Jun 12 2021