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 1-4 of 4 results.

A002840 Number of polyhedral graphs with n edges.

Original entry on oeis.org

1, 0, 1, 2, 2, 4, 12, 22, 58, 158, 448, 1342, 4199, 13384, 43708, 144810, 485704, 1645576, 5623571, 19358410, 67078828, 233800162, 819267086, 2884908430, 10204782956, 36249143676, 129267865144, 462669746182, 1661652306539, 5986979643542
Offset: 6

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Author

Keywords

References

  • M. B. Dillencourt, Polyhedra of small orders and their Hamiltonian properties. Tech. Rep. 92-91, Info. and Comp. Sci. Dept., Univ. Calif. Irvine, 1992.
  • 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).
  • T. R. S. Walsh, personal communication.

Crossrefs

Programs

  • PARI
    \\ It is assumed that the 3cp.gp file (from the linked zip archive) has been read before, i.e., \r [path]3cp.gp
    for(k=6,#ThreeConnectedData,print1(#ThreeConnectedData[k],", "));
    \\ printing of the edge lists of the graphs for n <= 11
    print(ThreeConnectedData[6..11]) \\ Hugo Pfoertner, Feb 14 2021

Extensions

a(30)-a(35) from the Numericana link added by Andrey Zabolotskiy, Jun 13 2020

A046091 Number of connected planar graphs with n edges.

Original entry on oeis.org

1, 1, 1, 3, 5, 12, 30, 79, 227, 709, 2318, 8049, 29372, 112000, 444855, 1833072, 7806724, 34252145, 154342391, 712231465, 3357126655, 16119421175, 78580665333
Offset: 0

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Author

Keywords

Comments

Inverse Euler transform of A343872. - Andrew Howroyd, May 05 2021

Examples

			a(3) = 3 since the three connected graphs with three edges are a path, a triangle and a "Y".
The first difference between this sequence and A002905 is for n=9 edges where we see K_{3,3}, the "utility graph".
		

Crossrefs

Row sums of A343873.
Column sums of A049334.

Programs

  • nauty
    # count graphs for the sequence by number of vertices v, sum over v afterwards
    geng -c $v $n:$n | planarg -q | countg -q # Georg Grasegger, Jul 06 2023

Extensions

a(11)-a(19) from Martin Fuller using nauty by Brendan McKay, Mar 07 2015
a(20)-a(22) added by Georg Grasegger, Jul 06 2023

A343870 Triangle read by rows: T(n,k) is the number of unlabeled nonseparable (or 2-connected) planar graphs with n edges and k nodes (n >= 1, 2 <= k <= n + 1).

Original entry on oeis.org

1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 3, 3, 1, 0, 0, 0, 0, 2, 9, 4, 1, 0, 0, 0, 0, 1, 13, 20, 6, 1, 0, 0, 0, 0, 0, 11, 49, 40, 7, 1, 0, 0, 0, 0, 0, 5, 77, 158, 70, 9, 1, 0, 0, 0, 0, 0, 2, 75, 406, 426, 121, 11, 1, 0, 0, 0, 0, 0, 0, 47, 662, 1645, 1018, 189, 13, 1, 0
Offset: 1

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Author

Andrew Howroyd, May 04 2021

Keywords

Examples

			Triangle T(n,k) begins (n edges >= 1, k vertices >= 2):
  1;
  0, 0;
  0, 1, 0;
  0, 0, 1, 0;
  0, 0, 1, 1,  0;
  0, 0, 1, 2,  1,  0;
  0, 0, 0, 3,  3,  1,   0;
  0, 0, 0, 2,  9,  4,   1,   0;
  0, 0, 0, 1, 13, 20,   6,   1,   0;
  0, 0, 0, 0, 11, 49,  40,   7,   1,  0;
  0, 0, 0, 0,  5, 77, 158,  70,   9,  1, 0;
  0, 0, 0, 0,  2, 75, 406, 426, 121, 11, 1, 0;
  ...
		

Crossrefs

Row sums are A343869.
Column sums are A021103.
Cf. A049334, A049336 (transpose), A049337, A253186, A339070.

Programs

  • nauty
    geng -C $k $n:$n | planarg -q | countg -q # Georg Grasegger, Jun 05 2023

Formula

T(n, n) = 1 for n >= 3.
T(n, n-1) = A253186(n-3) for n >= 3.

A289471 Number of planar strictly 2-connected graphs on n edges.

Original entry on oeis.org

1, 0, 1, 1, 2, 3, 7, 15, 39, 106, 316, 1030, 3553, 13006, 49780, 197281, 804649, 3358885, 14289507, 61769577
Offset: 1

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Author

Ed Pegg Jr, Jul 06 2017

Keywords

Crossrefs

Formula

a(n) = A343869(n) - A002840(n). - Andrew Howroyd, May 04 2021

Extensions

a(12)-a(13) corrected and a(14)-a(20) from Andrew Howroyd, May 04 2021
Showing 1-4 of 4 results.