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A133206
Number of unlabeled graphs with n nodes and a degenerate adjacency matrix.
1
1, 1, 3, 7, 25, 99, 690, 6551, 133174, 4138641, 290045659
OFFSET
1,3
COMMENTS
a(n) = A000088(n) - A109717(n)
LINKS
Ali Sltan Ali AL-Tarimshawy, J. Siemons, Singular Graphs with Dihedral Group Action, arXiv:2006.12875 [math.CO], 2020.
MATHEMATICA
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
CROSSREFS
Sequence in context: A120540 A176829 A352385 * A054092 A096648 A156100
KEYWORD
more,nonn
AUTHOR
Tanya Khovanova, Aug 27 2008
STATUS
approved