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Number of unlabeled graphs with n nodes and an invertible adjacency matrix.
3

%I #13 Aug 31 2017 04:03:54

%S 0,1,1,4,9,57,354,5795,141494,7866527,728952205

%N Number of unlabeled graphs with n nodes and an invertible adjacency matrix.

%t k = {}; For[i = 1, i < 8, i++, lg = ListGraphs[i] ; len = Length[lg]; k = Append[k, Length[Select[Range[len], Det[ToAdjacencyMatrix[lg[[ # ]]]] != 0 &]]]]; k

%K hard,more,nonn

%O 1,4

%A _Tanya Khovanova_, Aug 17 2008

%E Terms a(8)-a(10) from _Steve Butler_, Jun 21 2013

%E Term a(11) from _Steve Butler_, Aug 21 2013