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 1-10 of 14 results. Next

A167160 Duplicate of A111361.

Original entry on oeis.org

0, 0, 0, 0, 1, 0, 1, 1, 2, 1, 5, 2, 8, 5, 12, 8, 25, 13, 30, 23, 51, 33, 76, 51, 109, 78, 144, 106, 218, 150, 274, 212, 382, 279, 499, 366, 650, 493, 815, 623, 1083, 800, 1305, 1020, 1653, 1261, 2045, 1554, 2505, 1946, 3008, 2322, 3713, 2829, 4354, 3418, 5233, 4063
Offset: 2

Views

Author

Jonathan Vos Post, Oct 29 2009

Keywords

A078666 Number of isomorphism classes of simple quadrangulations of the sphere having n+2 vertices and n faces, minimal degree 3, with orientation-reversing isomorphisms permitted.

Original entry on oeis.org

1, 0, 1, 1, 3, 3, 12, 19, 64, 155, 510, 1514, 5146, 16966, 58782, 203269, 716607, 2536201, 9062402, 32533568, 117498072, 426212952, 1553048548, 5681011890, 20858998805, 76850220654, 284057538480, 1053134292253, 3915683667721
Offset: 6

Views

Author

Slavik V. Jablan and Brendan McKay Feb 06 2003

Keywords

Comments

Number of basic polyhedra with n vertices.
Initial terms of sequence coincide with A007022. Starting from n=12, to it is added the number of simple 4-regular 4-edge-connected but not 3-connected plane graphs on n nodes (A078672). As a result we obtain the number of basic polyhedra.
a(n) counts 4-valent 4-edge-connected planar maps (or plane graphs on a sphere) up to reflection with no regions bounded by just 2 edges. Conway called such maps "basic polyhedra" and used them in his knot notation. 2-edge-connected maps (which start occurring from n=12) are not taken into account here because they generate only composite knots and links. - Andrey Zabolotskiy, Sep 18 2017

Examples

			G.f. = x^6 + x^8 + x^9 + 3*x^10 + 3*x^11 + 12*x^12 + 19*x^13 + 64*x^14 + ...
From _Allan Bickle_, May 13 2024: (Start)
For n=6, the unique graph is the octahedron.
For n=8, the unique graph is the square of an 8-cycle.
For n=9, the unique graph is the dual of the Herschel graph. (End)
		

References

  • J. H. Conway, An enumeration of knots and links and some of their related properties. Computational Problems in Abstract Algebra, Proc. Conf. Oxford 1967 (Ed. J. Leech), 329-358. New York: Pergamon Press, 1970.

Crossrefs

Cf. A292515 (abstract planar graphs with same restrictions).

Extensions

Name and offset corrected by Andrey Zabolotskiy, Aug 22 2017

A007022 Number of 4-regular polyhedra with n nodes.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 1, 1, 3, 3, 11, 18, 58, 139, 451, 1326, 4461, 14554, 49957, 171159, 598102, 2098675, 7437910, 26490072, 94944685, 341867921, 1236864842, 4493270976, 16387852863, 59985464681, 220320405895, 811796327750, 3000183106119
Offset: 1

Views

Author

N. J. A. Sloane, Apr 28 1994

Keywords

Comments

Number of simple 4-regular 4-edge-connected 3-connected planar graphs; by Steinitz's theorem, every such graph corresponds to a single planar map up to orientation-reversing isomorphism. Equivalently, number of 3-connected quadrangulations of sphere with orientation-reversing isomorphisms permitted with n faces. - Andrey Zabolotskiy, Aug 22 2017

Examples

			For n=6, the sole 6-vertex 4-regular polyhedron is the octahedron. The corresponding 6-face quadrangulation is its dual graph, i. e., the cube graph.
From _Allan Bickle_, May 13 2024: (Start)
For n=8, the unique graph is the square of an 8-cycle.
For n=9, the unique graph is the dual of the Herschel graph. (End)
		

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A000944 (all polyhedral graphs), A113204, A078672, A078666 (total number of simple 4-regular 4-edge-connected planar maps, including not 3-connected ones).
Cf. A072552, A078666, A111361, A292515 (4-regular planar graphs with restrictions).

Extensions

More terms from Hugo Pfoertner, Mar 22 2003
a(29) corrected by Brendan McKay, Jun 22 2006
Leading zeros prepended by Max Alekseyev, Sep 12 2016
Offset corrected by Andrey Zabolotskiy, Aug 22 2017

A167156 Number of n-vertex 4-hedrites.

Original entry on oeis.org

1, 0, 2, 0, 2, 0, 4, 0, 3, 0, 5, 0, 3, 0, 7, 0, 5, 0, 7, 0, 4, 0, 11, 0, 5, 0, 8, 0, 8, 0, 12, 0, 6, 0, 13, 0, 6, 0, 15, 0, 10, 0, 11, 0, 7, 0, 21, 0, 10, 0, 13, 0, 12, 0, 18, 0, 9, 0, 22, 0, 9, 0, 21, 0, 14, 0, 16, 0, 14
Offset: 2

Views

Author

Jonathan Vos Post, Oct 29 2009

Keywords

Comments

Is this the same as A145393 alternating with zeros? - Andrey Zabolotskiy, Jul 05 2017

Examples

			Although every other term is zero, this sequence should be kept, contrary to the usual OEIS rules, to be analogous to the related sequences.
		

Crossrefs

A167158 Number of n-vertex 6-hedrites.

Original entry on oeis.org

0, 0, 1, 1, 2, 1, 5, 5, 9, 7, 14, 14, 23, 17, 28, 27, 44, 35, 54, 57, 77, 59, 87, 85, 119, 105, 134, 135, 187, 149, 189, 197, 251, 218, 278, 275, 354, 313, 361, 359, 472, 405, 480, 511, 609, 519, 613, 614, 771, 704, 771, 788, 989, 849, 938, 1005, 1175, 1038, 1215
Offset: 2

Views

Author

Jonathan Vos Post, Oct 29 2009

Keywords

Comments

A k-hedrite is a 4-regular planar graph whose faces have sizes 2, 3 and 4 only and the total number of faces of sizes 2 and 3 is k.

Crossrefs

Extensions

New name from Andrey Zabolotskiy, Jul 05 2017

A167159 Number of n-vertex 7-hedrites.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 1, 1, 3, 4, 5, 7, 9, 12, 18, 22, 25, 36, 46, 48, 62, 76, 88, 107, 126, 142, 179, 198, 216, 257, 304, 329, 382, 431, 483, 547, 601, 643, 764, 838, 889, 998, 1134, 1197, 1324, 1435, 1574, 1751, 1874, 1963, 2247, 2419, 2511, 2735, 3041, 3187, 3453
Offset: 2

Views

Author

Jonathan Vos Post, Oct 29 2009

Keywords

Comments

A k-hedrite is a 4-regular planar graph whose faces have sizes 2, 3 and 4 only and the total number of faces of sizes 2 and 3 is k.

Crossrefs

Extensions

New name from Andrey Zabolotskiy, Jul 05 2017

A167157 Number of n-vertex 5-hedrites.

Original entry on oeis.org

0, 1, 0, 1, 2, 3, 1, 2, 3, 5, 3, 4, 7, 10, 6, 6, 7, 12, 9, 8, 15, 20, 11, 12, 16, 21, 18, 16, 24, 32, 24, 18, 26, 37, 23, 24, 38, 45, 37, 30, 33, 52, 44, 34, 56, 69, 45, 40, 54, 66, 58, 48, 66, 92, 68, 49, 71, 98, 70, 63, 96, 104, 92, 74, 80, 122, 98, 72, 120
Offset: 2

Views

Author

Jonathan Vos Post, Oct 29 2009

Keywords

Comments

A k-hedrite is a 4-regular planar graph whose faces have sizes 2, 3 and 4 only and the total number of faces of sizes 2 and 3 is k.

Crossrefs

Extensions

New name from Andrey Zabolotskiy, Jul 05 2017

A072552 Number of connected planar regular graphs of degree 4 with n nodes.

Original entry on oeis.org

1, 0, 1, 1, 3, 3, 13, 21, 68, 166, 543, 1605, 5413, 17735, 61084, 210221, 736287
Offset: 6

Views

Author

Markus Meringer (meringer(AT)uni-bayreuth.de), Aug 05 2002

Keywords

Comments

Numbers were obtained using the graph generator GENREG in combination with a test for planarity implemented by M. Raitner.

Examples

			From _Allan Bickle_, May 13 2024: (Start)
For n=6, the unique graph is the octahedron.
For n=8, the unique graph is the square of an 8-cycle.
For n=9, the unique graph is the dual of the Herschel graph. (End)
		

Crossrefs

Cf. A005964, A006820, A078666, A292515 (4-edge-connected graphs only).
Cf. A007022, A111361 (other 4-regular planar graphs).

Extensions

a(19)-a(22) from Andrey Zabolotskiy, Mar 21 2018 from Tuzun & Sikora.

A167227 Number of 2-self-hedrites with n vertices.

Original entry on oeis.org

1, 1, 2, 2, 3, 3, 3, 3, 5, 4, 4, 6, 5, 5, 8, 5, 6, 8, 6, 8, 10, 7, 7, 10, 10, 8, 12, 10, 9, 14, 9, 9, 14, 10, 14, 16, 11, 11, 16
Offset: 2

Views

Author

Jonathan Vos Post, Oct 30 2009

Keywords

Comments

A 2-self-hedrite is a self-dual plane multigraph such that each its face has 4 sides except for 2 faces with 2 sides. - Andrey Zabolotskiy, Dec 16 2021

Crossrefs

Formula

It appears that a(n+1) = A167156(2*n) - A167156(n) [discovered using Sequence Machine]. An equivalent assertion is that if a plane multigraph and its dual both have only 4-gonal faces except for 2 2-gonal ones, then they are isomorphic. - Andrey Zabolotskiy, Dec 16 2021

A292515 Number of 4-regular 4-edge-connected planar simple graphs on n vertices.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 1, 1, 3, 3, 12, 19, 63, 153, 499, 1473, 4974, 16296, 56102, 192899, 674678, 2381395, 8468424
Offset: 1

Views

Author

Andrey Zabolotskiy, Sep 18 2017

Keywords

Comments

The difference between this sequence and A078666 arises because the latter lists not abstract planar graphs but plane graphs (on the sphere, with the same restrictions). Among A078666(14)=64 plane graphs there is 1 pair of isomorphic graphs, namely graphs No. 63 and 64 (hereafter the enumeration of plane graphs from the LinKnot Mathematica package is used, see The Knot Atlas link), hence a(14)=64-1=63. Among 155 plane graphs on 15 vertices, the isomorphic pairs are (143, 149) and (153, 155), hence a(15)=155-2=153. The 11 isomorphic pairs of plane graphs on 16 vertices are: (456, 492), (459, 493), (464, 496), (465, 501), (466, 468), (470, 487), (473, 503), (477, 488), (478, 479), (486, 497), (498, 504).
Tuzun and Sikora say that such planar graphs constitute the set of 4-edge-connected basic Conway polyhedra, and indeed it suffices to consider any one embedding of each of these graphs into sphere or plane to list all prime knots. However, usually the set of Conway polyhedra is identified with the set of plane graphs instead (see A078666 and references therein), which is necessary to list or encode all prime knot diagrams (on the sphere).

Examples

			From _Allan Bickle_, May 13 2024: (Start)
For n=6, the unique graph is the octahedron.
For n=8, the unique graph is the square of an 8-cycle.
For n=9, the unique graph is the dual of the Herschel graph. (End)
		

Crossrefs

Cf. A007022, A072552, A078666, A111361 (4-regular planar graphs with restrictions).

Extensions

a(23)-a(24) added from Tuzun & Sikora (2020) by Andrey Zabolotskiy, Apr 27 2020
Showing 1-10 of 14 results. Next