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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = A000088(n) - A109717(n)

LINKS

Table of n, a(n) for n=1..11.

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

Cf. A000088, A109717.

Sequence in context: A096579 A120540 A176829 * A054092 A096648 A156100

Adjacent sequences:  A133203 A133204 A133205 * A133207 A133208 A133209

KEYWORD

more,nonn

AUTHOR

Tanya Khovanova, Aug 27 2008

STATUS

approved

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Last modified February 18 09:15 EST 2020. Contains 332011 sequences. (Running on oeis4.)