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 1-5 of 5 results.

A002851 Number of unlabeled trivalent (or cubic) connected simple graphs with 2n nodes.

Original entry on oeis.org

1, 0, 1, 2, 5, 19, 85, 509, 4060, 41301, 510489, 7319447, 117940535, 2094480864, 40497138011, 845480228069, 18941522184590, 453090162062723, 11523392072541432, 310467244165539782, 8832736318937756165
Offset: 0

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Keywords

Examples

			G.f. = 1 + x^2 + 2*x^3 + 5*x^4 + 19*x^5 + 85*x^6 + 509*x^7 + 4060*x^8 + 41302*x^9 + 510489*x^10 + 7319447*x^11 + ...
a(0) = 1 because the null graph (with no vertices) is vacuously 3-regular.
a(1) = 0 because there are no simple connected cubic graphs with 2 nodes.
a(2) = 1 because the tetrahedron is the only cubic graph with 4 nodes.
a(3) = 2 because there are two simple cubic graphs with 6 nodes: the bipartite graph K_{3,3} and the triangular prism graph.
		

References

  • CRC Handbook of Combinatorial Designs, 1996, p. 647.
  • F. Harary, Graph Theory. Addison-Wesley, Reading, MA, 1969, p. 195.
  • R. C. Read, Some applications of computers in graph theory, in L. W. Beineke and R. J. Wilson, editors, Selected Topics in Graph Theory, Academic Press, NY, 1978, pp. 417-444.
  • R. C. Read and G. F. Royle, Chromatic roots of families of graphs, pp. 1009-1029 of Y. Alavi et al., eds., Graph Theory, Combinatorics and Applications. Wiley, NY, 2 vols., 1991.
  • R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence)

Crossrefs

Cf. A004109 (labeled connected cubic), A361407 (rooted connected cubic), A321305 (signed connected cubic), A000421 (connected cubic loopless multigraphs), A005967 (connected cubic multigraphs), A275744 (multisets).
Contribution (almost all) from Jason Kimberley, Feb 10 2011: (Start)
3-regular simple graphs: this sequence (connected), A165653 (disconnected), A005638 (not necessarily connected), A005964 (planar).
Connected regular graphs A005177 (any degree), A068934 (triangular array), specified degree k: this sequence (k=3), A006820 (k=4), A006821 (k=5), A006822 (k=6), A014377 (k=7), A014378 (k=8), A014381 (k=9), A014382 (k=10), A014384 (k=11).
Connected 3-regular simple graphs with girth at least g: A185131 (triangle); chosen g: this sequence (g=3), A014371 (g=4), A014372 (g=5), A014374 (g=6), A014375 (g=7), A014376 (g=8).
Connected 3-regular simple graphs with girth exactly g: A198303 (triangle); chosen g: A006923 (g=3), A006924 (g=4), A006925 (g=5), A006926 (g=6), A006927 (g=7). (End)

Extensions

More terms from Ronald C. Read

A321304 Triangle T(n,f): the number of bicolored connected cubic graphs on 2n vertices with f vertices of the first color.

Original entry on oeis.org

1, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 5, 5, 5, 2, 2, 5, 10, 31, 46, 63, 46, 31, 10, 5, 19, 64, 248, 542, 931, 1052, 931, 542, 248, 64, 19, 85, 490, 2382, 7011, 15199, 23405, 27336, 23405, 15199, 7011, 2382, 490, 85, 509, 4595, 27233, 101002, 268675, 523246, 776657, 882321, 776657, 523246, 268675, 101002, 27233, 4595, 509
Offset: 0

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Author

R. J. Mathar, Nov 03 2018

Keywords

Comments

These are connected, undirected, simple cubic graphs where each vertex has either the first or the second color. Row n has 2n+1 entries, 0<=f<=2n. The column f=0 (1, 0, 2, 5,...) counts the cubic graphs (A002851). The column f=1 (0, 1, 2, 10, 64, 490...) counts the rooted cubic graphs.

Examples

			The triangle starts:
0 vertices:   1;
2 vertices:   0,  0,   0;
4 vertices:   1,  1,   1,   1,   1;
6 vertices:   2,  2,   5,   5,   5,    2,   2;
8 vertices:   5, 10,  31,  46,  63,   46,  31,  10,   5;
10 vertices: 19, 64, 248, 542, 931, 1052, 931, 542, 248, 64, 19;
		

Crossrefs

Columns f=0, 1, 2 are A002851, A361407, A361408.
Row sums are A361403.
Central coefficients are A361406.
Cf. A294783 (bicolored trees), A321305 (signed edges), A361361 (not necessarily connected).

Formula

T(n,f) = T(n,2n-f).

Extensions

Terms a(49) and beyond from Andrew Howroyd, Mar 11 2023

A361408 Number of connected cubic graphs on 2n unlabeled vertices rooted at a pair of indistinguishable vertices.

Original entry on oeis.org

0, 1, 5, 31, 248, 2382, 27233, 359800, 5364193, 88622485, 1602171855, 31410476113, 663240471075, 15001046054183, 361775504849332, 9266474332849318, 251217335356943672, 7186461542458525108, 216332059500870350414, 6835872042063656823802
Offset: 1

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Author

Andrew Howroyd, Mar 11 2023

Keywords

Crossrefs

Column k=2 of A321304.

Formula

G.f.: B(x)/C(x) - (D(x) + D(x^2))/2 where B(x), C(x) and D(x) are the g.f.s of A361411, A005638 and A361407, respectively.

A361410 Number of cubic graphs on 2n unlabeled vertices rooted at a vertex.

Original entry on oeis.org

0, 1, 2, 11, 68, 510, 4712, 51877, 664520, 9662968, 156490473, 2783955994, 53863486240, 1124886942314, 25206326633070, 603048386506505, 15339533779133582, 413338072569232815, 11760801736217845686, 352342902996056683824
Offset: 1

Views

Author

Andrew Howroyd, Mar 11 2023

Keywords

Crossrefs

Column k=1 of A361361.

A361406 Number of bicolored connected cubic graphs on 2n unlabeled vertices with n vertices of each color.

Original entry on oeis.org

1, 0, 1, 5, 63, 1052, 27336, 882321, 34455134, 1558650424, 80016369538, 4589908631503, 290839634055722, 20171917072658395, 1519875854413728667, 123616508830454828043, 10794216583730162449785, 1007179737486515827821590, 100007950522974604304016627, 10529173417583858651114779790, 1171605981584666223513790021758
Offset: 0

Views

Author

Andrew Howroyd, Mar 11 2023

Keywords

Comments

Adjacent vertices may have the same color.

Examples

			a(1) = 1 since the only cubic graph on 4 vertices is the complete graph. The bicolored graphs are indistinguishable whichever 2 vertices are colored in the first color.
		

Crossrefs

Central coefficients of A321304.
Showing 1-5 of 5 results.