A219893 -id:A219893 - cp's OEIS frontend

A219889 Number of directed 2-regular graphs on n nodes.

1, 2, 5, 23, 92, 624, 5021, 47034, 494320, 5719769, 71971687

Offset: 3

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.
R. J. Mathar, OEIS A219889
Richard J. Mathar, 2-regular Digraphs of the Lovelock Lagrangian, arXiv:1903.12477 [math.GM], 2019.

Column k=2 of A350910.

Cf. A096368, A219890, A219891, A219892, A219893, A307155 (connected, inverse Euler Trans.), A007107 (labeled), A306827 (multiedges, connected), A002865 (directed 1-regular unlabeled no loops), A005641 (loops allowed)

A219890 Number of directed 3-regular graphs on n nodes.

Original entry on oeis.org

1, 2, 23, 415, 19041, 1104045, 79818336, 6958257941, 720814138673, 87579097910309

Offset: 4

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Column k=3 of A350910.

Cf. A096368, A219889, A219890, A219891, A219892, A219893.

A219891 Number of directed 4-regular graphs on n nodes.

Original entry on oeis.org

1, 4, 92, 19041, 6510087, 2983458766, 1775668832509, 1349509467853512

Offset: 5

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Column k=4 of A350910.

Cf. A096368, A219889, A219890, A219892, A219893.

A219892 Number of directed 5-regular graphs on n nodes.

Original entry on oeis.org

1, 4, 624, 1104045, 2983458766, 10922621656743

Offset: 6

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Column k=5 of A350910.

Cf. A096368, A219889, A219890, A219891, A219893.

A350910 Triangle read by rows: T(n,k) is the number of k-regular digraphs on n unlabeled nodes, k = 0..n-1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 5, 2, 1, 1, 4, 23, 23, 4, 1, 1, 4, 92, 415, 92, 4, 1, 1, 7, 624, 19041, 19041, 624, 7, 1, 1, 8, 5021, 1104045, 6510087, 1104045, 5021, 8, 1, 1, 12, 47034, 79818336, 2983458766, 2983458766, 79818336, 47034, 12, 1

Offset: 1

Andrew Howroyd, Jan 29 2022

			Triangle begins:
  1;
  1, 1;
  1, 1,   1;
  1, 2,   2,     1;
  1, 2,   5,     2,     1;
  1, 4,  23,    23,     4,   1;
  1, 4,  92,   415,    92,   4, 1;
  1, 7, 624, 19041, 19041, 624, 7, 1;
  ...

Columns k=0..6 are A000012, A002865, A219889, A219890, A219891, A219892, A219893.
Row sums are A350911.
Cf. A051031 (graphs), A329228 (semi-regular), A350912.

A219894 Number of directed 2-regular graphs on n nodes without directed 2-cycles.

Original entry on oeis.org

1, 4, 9, 55, 453, 4357, 47598, 569769, 7371560, 102525991, 1525164223

Offset: 5

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Cf. A096368, A219889, A219890, A219891, A219892, A219893, A219895.

a(14) and a(15) from Brendan McKay, Mar 12 2019

A219895 Number of directed 3-regular graphs on n nodes without directed 2-cycles.

Original entry on oeis.org

3, 26, 1547, 146487, 16018987, 1985766270, 278601715904

Offset: 7

N. J. A. Sloane, Nov 30 2012

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Cf. A096368, A219889, A219890, A219891, A219892, A219893, A219894.

cp's OEIS Frontend

A219889 Number of directed 2-regular graphs on n nodes.

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A219890 Number of directed 3-regular graphs on n nodes.

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A219891 Number of directed 4-regular graphs on n nodes.

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A219892 Number of directed 5-regular graphs on n nodes.

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A350910 Triangle read by rows: T(n,k) is the number of k-regular digraphs on n unlabeled nodes, k = 0..n-1.

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A219894 Number of directed 2-regular graphs on n nodes without directed 2-cycles.

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A219895 Number of directed 3-regular graphs on n nodes without directed 2-cycles.

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