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 1-2 of 2 results.

A066537 Number of planar graphs on n labeled nodes.

Original entry on oeis.org

1, 1, 2, 8, 64, 1023, 32071, 1823707, 163947848, 20402420291, 3209997749284, 604611323732576, 131861300077834966, 32577569614176693919, 8977083127683999891824, 2726955513946123452637877, 904755724004585279250537376, 325403988657293080813790670641
Offset: 0

Views

Author

Aart Blokhuis (aartb(AT)win.tue.nl), Jan 08 2002

Keywords

Comments

Precise numbers derived from numbers of 3-connected, 2-connected and 1-connected planar labeled graphs. Details and more entries in Bodirsky et al. Some bounds on the asymptotics are known, see e.g. Taraz et al.

References

  • Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, p. 419.

Crossrefs

Programs

  • PARI
    Q(n,k) = { \\ c-nets with n-edges, k-vertices
      if (k < 2+(n+2)\3 || k > 2*n\3, return(0));
      sum(i=2, k, sum(j=k, n, (-1)^((i+j+1-k)%2)*binomial(i+j-k,i)*i*(i-1)/2*
      (binomial(2*n-2*k+2,k-i)*binomial(2*k-2, n-j) -
      4*binomial(2*n-2*k+1, k-i-1)*binomial(2*k-3, n-j-1))));
    };
    A100960_ser(N) = {
    my(x='x+O('x^(3*N+1)), t='t+O('t^(N+4)),
       q=t*x*Ser(vector(3*N+1, n, Polrev(vector(min(N+3, 2*n\3), k, Q(n,k)),'t))),
       d=serreverse((1+x)/exp(q/(2*t^2*x) + t*x^2/(1+t*x))-1),
       g2=intformal(t^2/2*((1+d)/(1+x)-1)));
       serlaplace(Ser(vector(N, n, subst(polcoeff(g2, n,'t),'x,'t)))*'x);
    };
    A096331_seq(N) = Vec(subst(A100960_ser(N+2),'t,1));
    A096332_seq(N) = {
      my(x='x+O('x^(N+3)), b=x^2/2+serconvol(Ser(A096331_seq(N))*x^3, exp(x)));
      Vec(serlaplace(intformal(serreverse(x/exp(b'))/x)));
    };
    A066537_seq(N) = {
      my(x='x+O('x^(N+3)));
      Vec(serlaplace(exp(serconvol(Ser(A096332_seq(N))*'x,exp(x)))));
    };
    A066537_seq(15) \\ Gheorghe Coserea, Aug 10 2017

Formula

Recurrence known, see Bodirsky et al.
a(n) ~ g * n^(-7/2) * gamma^n * n!, where g=0.000004260938569161439...(A266391) and gamma=27.2268777685...(A266390) (see Gimenez and Noy).

Extensions

More terms from Manuel Bodirsky (bodirsky(AT)informatik.hu-berlin.de), Sep 15 2003
Entry revised by N. J. A. Sloane, Jun 17 2006

A343871 Number of labeled 3-connected planar graphs with n edges.

Original entry on oeis.org

1, 0, 15, 70, 432, 4320, 30855, 294840, 2883240, 28175952, 310690800, 3458941920, 40459730640, 499638948480, 6324655705200, 83653192972800, 1145266802114400, 16145338385736000, 235579813593453000, 3535776409508703360, 54571687068401395200, 866268656574795936000
Offset: 6

Views

Author

Andrew Howroyd, May 05 2021

Keywords

Crossrefs

Cf. A000287, A002840 (unlabeled case), A096330, A290326, A291841, A338414.

Programs

  • PARI
    Q(n,k) = { \\ c-nets with n-edges, k-vertices (see A290326)
      if (k < 2+(n+2)\3 || k > 2*n\3, return(0));
      sum(i=2, k, sum(j=k, n, (-1)^((i+j+1-k)%2)*binomial(i+j-k,i)*i*(i-1)/2*
      (binomial(2*n-2*k+2,k-i)*binomial(2*k-2, n-j) -
      4*binomial(2*n-2*k+1, k-i-1)*binomial(2*k-3, n-j-1))));
    };
    a(n)={sum(k=2+(n+2)\3, 2*n\3, k!*Q(n,k))/(4*n)} \\ Andrew Howroyd, May 05 2021

Formula

a(n) = Sum_{k=2+floor((n+2)/3)..floor(2*n/3)} k!*A290326(n-k+1, k-1)/(4*n).
Showing 1-2 of 2 results.