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 13 results. Next

A113204 Same as A007022, but with orientation-reversing isomorphisms forbidden.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 1, 1, 4, 3, 15, 25, 92, 234, 803, 2469, 8512, 28290, 98148, 338673, 1188338, 4180854, 14840031, 52904562, 189724510, 683384218, 2472961423, 8984888982, 32772085447, 119963084542, 440623586740, 1623555117611
Offset: 1

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Author

N. J. A. Sloane, Jan 07 2006

Keywords

Crossrefs

Extensions

a(29) corrected by Brendan McKay, Jun 22 2006
Leading zeros prepended by Max Alekseyev, Sep 13 2016
Offset corrected by Andrey Zabolotskiy, Feb 09 2018

A111361 The number of 4-regular plane graphs with n vertices with all faces 3-gons or 4-gons.

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, 6234
Offset: 2

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Author

Gunnar Brinkmann, Nov 07 2005

Keywords

Comments

These are the 4-regular graphs corresponding to the 3-regular fullerenes. Only the two smallest possible face sizes are allowed. The numbers up to a(33) have been checked by 2 independent programs. Further numbers have not been checked independently.

Examples

			From _Allan Bickle_, May 13 2024: (Start)
The smallest example (n=6) is the octahedron (only 3-gons).
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. A007894.
Cf. A007022, A072552, A078666, A292515 (4-regular planar graphs with restrictions).

Extensions

Leading zeros prepended, terms a(34) and beyond added from the book by Deza et al. (except for a(60) from the paper by Brinkmann et al.) by Andrey Zabolotskiy, Oct 09 2021

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

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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

A002880 Number of 3-connected nets with n edges.

Original entry on oeis.org

1, 0, 1, 1, 2, 2, 9, 11, 37, 79, 249, 671, 2182, 6692, 22131, 72405, 243806, 822788, 2815119, 9679205, 33551192, 116900081, 409675567, 1442454215, 5102542680, 18124571838, 64634480340, 231334873091, 830828150081, 2993489821771
Offset: 6

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Author

Keywords

Comments

Also, the number of 3-connected quadrangulations without separating 4-cycles (up to orientation) with n faces. - Andrey Zabolotskiy, Sep 20 2019

Examples

			G.f. = x^6 + x^8 + x^9 + 2*x^10 + 2*x^11 + 9*x^12 + 11*x^13 + 37*x^14 + ...
		

References

  • 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

A113201 Number of isomorphism classes of simple quadrangulations of the sphere having n vertices and n-2 faces, with orientation-reversing isomorphisms permitted.

Original entry on oeis.org

1, 1, 2, 3, 9, 18, 62, 198, 803, 3378, 15882, 77185, 393075, 2049974, 10938182, 59312272, 326258544, 1815910231, 10213424233, 57974895671, 331820721234, 1913429250439, 11109119321058, 64901418126997
Offset: 4

Views

Author

N. J. A. Sloane, Jan 07 2006

Keywords

Crossrefs

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

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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.

A113205 Same as A002880, but with orientation-reversing isomorphisms forbidden.

Original entry on oeis.org

1, 0, 1, 1, 3, 2, 12, 16, 59, 133, 445, 1248, 4162, 13014, 43474, 143304, 484444, 1639388, 5617205, 19332596, 67048051, 233691112, 819121608, 2884443024, 10204104900, 36247138920, 129264732757, 462661038926, 1661637913984
Offset: 6

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Author

N. J. A. Sloane, Jan 07 2006

Keywords

Crossrefs

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

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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

A113202 Number of isomorphism classes of simple quadrangulations of the sphere having n vertices and n-2 faces, with orientation-reversing isomorphisms forbidden.

Original entry on oeis.org

1, 1, 2, 3, 10, 21, 83, 298, 1339, 6049, 29765, 148842, 770267, 4054539, 21743705, 118237471, 651370528, 3628421181, 20416662314, 115919209155, 663548898942, 3826577783917, 22217382001865, 129800215435088
Offset: 4

Views

Author

N. J. A. Sloane, Jan 07 2006

Keywords

Crossrefs

A078672 Number of simple 4-regular 4-edge-connected but not 3-connected plane graphs on n nodes.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 1, 1, 6, 16, 59, 188, 685, 2412, 8825, 32110, 118505, 437526, 1624492, 6043496, 22553387, 84345031, 316183706, 1187740914, 4471145942, 16864755973, 63737132585, 241337964503, 915500561602
Offset: 6

Views

Author

Slavik V. Jablan and Brendan McKay, Feb 06 2003

Keywords

Examples

			The first such graph has 12 nodes. It is called 12E [Jablan, Radović & Sazdanović, Fig. 2; or Caudron, p. 308c] and looks like that:
    ___________
   /           \
  / O---O   O---O
  |/|\ /|\ /|\ /|
  O | O | O | O |
  |\|/ \|/ \|/ \|
  \ O---O   O---O
   \___________/
		

Crossrefs

Formula

a(n) = A078666(n) - A007022(n).

Extensions

a(23)-a(34) from Sean A. Irvine, Jul 09 2025
Showing 1-10 of 13 results. Next