cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A141040 Number of graphs with 2n vertices that have an odd determinant for their adjacency matrix.

Original entry on oeis.org

1, 4, 47, 4043, 4553432
Offset: 1

Views

Author

Tanya Khovanova, Aug 18 2008

Keywords

Crossrefs

Cf. A000088, A140981.

Extensions

a(4)-a(5) from Andrew Howroyd, Nov 04 2017

A103869 Number of unlabeled graphs with n nodes whose adjacency matrix has nonzero even determinant.

Original entry on oeis.org

0, 0, 1, 0, 9, 10, 354, 1752, 141494, 3313095, 728952205
Offset: 1

Views

Author

Tanya Khovanova, Aug 29 2008

Keywords

Crossrefs

Cf. A133206, A140981, A141040, A109717, A000088.

Programs

  • 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 && Mod[Det[ToAdjacencyMatrix[lg[[ # ]]]], 2] == 0 &]]]]; k

Formula

a(n) = A140981(n) - A133206(n).
For odd n, a(n) = A109717(n). For even n, a(n) = A109717(n) - A141040(n/2). - Max Alekseyev, Feb 20 2024

Extensions

a(8)-a(10) from Andrew Howroyd, Nov 04 2017
a(11) from A109717 added by Max Alekseyev, Feb 20 2024
Showing 1-2 of 2 results.

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