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.

A005470 Number of unlabeled planar simple graphs with n nodes.

Original entry on oeis.org

1, 1, 2, 4, 11, 33, 142, 822, 6966, 79853, 1140916, 18681008, 333312451
Offset: 0

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Author

Keywords

Comments

Euler transform of A003094. - Christian G. Bower

Examples

			a(2) = 2 since o o and o-o are the two planar simple graphs on two nodes.
		

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • W. T. Trotter, ed., Planar Graphs, Vol. 9, DIMACS Series in Discrete Mathematics and Theoretical Computer Science, Amer. Math. Soc., 1993.
  • Turner, James; Kautz, William H. A survey of progress in graph theory in the Soviet Union. SIAM Rev. 12 1970 suppl. iv+68 pp. MR0268074 (42 #2973). See p. 19. - N. J. A. Sloane, Apr 08 2014
  • Vetukhnovskii, F. Ya. "Estimate of the Number of Planar Graphs." In Soviet Physics Doklady, vol. 7, pp. 7-9. 1962. - From N. J. A. Sloane, Apr 08 2014
  • R. J. Wilson, Introduction to Graph Theory. Academic Press, NY, 1972, p. 162.

Crossrefs

Cf. A003094 (connected planar graphs), A034889, A039735 (planar graphs by nodes and edges).
Cf. A126201.

Programs

  • Mathematica
    A003094 = Cases[Import["https://oeis.org/A003094/b003094.txt", "Table"], {, }][[All, 2]];
    (* EulerTransform is defined in A005195 *)
    EulerTransform[Rest @ A003094] (* Jean-François Alcover, Apr 25 2013, updated Mar 17 2020 *)

Extensions

n=8 term corrected and n=9..11 terms calculated by Brendan McKay
Terms a(0) - a(10) confirmed by David Applegate and N. J. A. Sloane, Mar 09 2007
a(12) added by Vaclav Kotesovec after A003094 (computed by Brendan McKay), Dec 06 2014

A003094 Number of unlabeled connected planar simple graphs with n nodes.

Original entry on oeis.org

1, 1, 1, 2, 6, 20, 99, 646, 5974, 71885, 1052805, 17449299, 313372298, 5942258308
Offset: 0

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Author

Keywords

Comments

Inverse Euler transform of A005470. - Christian G. Bower, May 16 2003

Examples

			a(3) = 2 since the path o-o-o and the triangle are the two connected planar simple graphs on three nodes.
		

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • R. J. Wilson, Introduction to Graph Theory, Academic Press, NY, 1972, p. 162.

Crossrefs

Row sums of A049334.
The labeled version is A096332.

Programs

  • Mathematica
    a[n_Integer?NonNegative] := a[n] = Module[{m, s, g}, s = Subsets[Range[n], {2}]; m = Length[s]; g = Graph[Range[n], UndirectedEdge @@@ #] & /@ (Pick[s, #, 1] & /@ (IntegerDigits[#, 2, m] & /@ Range[0, 2^m - 1])); Length[DeleteDuplicates[Select[Select[g, ConnectedGraphQ], PlanarGraphQ], IsomorphicGraphQ]]]; Table[a[n], {n, 0, 6}] (* Robert P. P. McKone, Oct 14 2023 *)
  • nauty
    geng -c $n | planarg -q | countg -q # Georg Grasegger, Jul 06 2023

Extensions

More terms from Brendan McKay
a(12) added by Brendan McKay, Dec 06 2014
a(13) added by Georg Grasegger, Jul 06 2023

A126100 Number of rooted connected unlabeled graphs on n nodes.

Original entry on oeis.org

0, 1, 1, 3, 11, 58, 407, 4306, 72489, 2111013, 111172234, 10798144310, 1944301471861, 650202565436890, 404697467417019634, 470133531223369393920, 1022561022228933341815171, 4177761667636803276899047351, 32163582481439081597751699343141, 468019937132164016636736323752098741
Offset: 0

Views

Author

David Applegate and N. J. A. Sloane, Mar 05 2007

Keywords

Comments

Let G run through all connected unlabeled graphs on n nodes. Add up the numbers of inequivalent nodes (under Aut(G)) for each G.
"Pointed" connected graphs. This has the same relation to A001349 as A000081 does to A000055.
a(0) = 0 because the empty graph cannot be rooted.

Examples

			For 3 nodes G is either a path (2 kinds of nodes) or a triangle (one kind of node), for a total of a(3) = 3.
For the 5-vertex graphs we have 2 * 1 orbit, 6 * 2 orbits, 8 * 3 orbits, 5 * 4 orbits for a total of 2 + 12 + 24 + 20 = 58.
		

Crossrefs

Programs

  • Mathematica
    permcount[v_] := Module[{m = 1, s = 0, k = 0, t}, For[i = 1, i <= Length[v], i++, t = v[[i]]; k = If[i > 1 && t == v[[i - 1]], k + 1, 1]; m *= t*k; s += t]; s!/m];
    edges[v_] := Sum[GCD[v[[i]], v[[j]]], {i, 2, Length[v]}, {j, 1, i - 1}] + Total[Quotient[v, 2]];
    g[n_, r_] := (s = 0; Do[s += permcount[p]*(2^(r*Length[p] + edges[p])), {p, IntegerPartitions[n]}]; s/n!);
    seq[m_] := Sum[g[n-1, 1] x^(n-1), {n, 0, m}]/Sum[g[n-1, 0] x^(n-1), {n, 0, m}] + O[x]^m // CoefficientList[#, x]& // Prepend[#, 0]&;
    seq[20] (* Jean-François Alcover, Jul 09 2018, after Andrew Howroyd *)
  • PARI
    permcount(v) = {my(m=1,s=0,k=0,t); for(i=1,#v,t=v[i]; k=if(i>1&&t==v[i-1],k+1,1); m*=t*k;s+=t); s!/m}
    edges(v) = {sum(i=2, #v, sum(j=1, i-1, gcd(v[i],v[j]))) + sum(i=1, #v, v[i]\2)}
    g(n,r) = {my(s=0); forpart(p=n, s+=permcount(p)*(2^(r*#p+edges(p)))); s/n!}
    seq(n)={concat([0], Vec(Ser(vector(n, n, g(n-1,1)))/Ser(vector(n, n, g(n-1,0)))))} \\ Andrew Howroyd, May 03 2018

Formula

The g.f. A(x) = x+x^2+3*x^3+11*x^4+... satisfies f(x) = 1 + A(x)*g(x), where f(x) = 1+x+2*x^2+6*x^3+20*x^4+... is the g.f. for A000666 and g(x) = 1+x+2*x^2+4*x^3+11*x^4+... is the g.f. for A000088. - Brendan McKay

Extensions

a(5)-a(9) computed by Gordon F. Royle, Mar 05 2007
a(10) and a(11) computed by Brendan McKay, Mar 05 2007
a(12) onwards computed from the generating function, A000088 and A000666 by David Applegate and N. J. A. Sloane, Mar 06 2007

A173422 Partials sums of A003094 (unlabeled connected planar simple graphs with n nodes).

Original entry on oeis.org

1, 2, 3, 5, 11, 31, 130, 776, 6750, 78635, 1131440, 18580739, 331953037
Offset: 0

Views

Author

Jonathan Vos Post, Feb 18 2010

Keywords

Comments

Partials sums of number of unlabeled connected planar simple graphs with n nodes. The subsequence of primes in these partial sums begins: 2, 3, 5, 11, 31.

Examples

			a(11) = 1 + 1 + 1 + 2 + 6 + 20 + 99 + 646 + 5974 + 71885 + 1052805 + 17449299.
		

Crossrefs

Cf. A003094, inverse Euler transform of A005470, A126201.

Programs

Formula

a(n) = Sum_{i=0..n} A003094(i).

Extensions

Edited and a(12) added by M. F. Hasler, Mar 20 2018
Showing 1-4 of 4 results.