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A050535 Number of multigraphs on infinite set of nodes with n edges. 42
1, 1, 3, 8, 23, 66, 212, 686, 2389, 8682, 33160, 132277, 550835, 2384411, 10709827, 49782637, 238998910, 1182772364, 6023860266, 31525780044, 169316000494, 932078457785, 5253664040426, 30290320077851, 178480713438362, 1073918172017297 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Also, a(n) is the number of n-rowed binary matrices with all row sums equal to 2, up to row and column permutation (see Jovovic's formula). Also, a(n) is the limit of A192517(m,n) as m grows. - Max Alekseyev, Oct 18 2017

Row sums of the triangle defined by the Multiset Transformation of A076864,

1 ;

0 1;

0 2 1;

0 5 2 1;

0 12 8 2 1;

0 33 22 8 2 1;

0 103 72 26 8 2 1;

0 333 229 87 26 8 2 1;

0 1183 782 295 92 26 8 2 1;

0 4442 2760 1036 315 92 26 8 2 1;

0 17576 10270 3735 1129 321 92 26 8 2 1;

0 72810 39770 13976 4117 1154 321 92 26 8 2 1;

0 314595 160713 54132 15547 4237 1161 321 92 26 8 2 1;

- R. J. Mathar, Jul 18 2017

Also the number of non-isomorphic set multipartitions (multisets of sets) of {1, 1, 2, 2, 3, 3, ..., n, n}. - Gus Wiseman, Jul 18 2018

REFERENCES

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 88, Eq. (4.1.18).

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..50

F. Harary, The number of linear, directed, rooted, and connected graphs, Trans. Am. Math. Soc. 78 (1955) 445-463, eq. (24).

V. Jovovic, Number of m-rowed binary matrices with all row sums equal to n, up to row and column permutation

Patrick T. Komiske, Eric M. Metodiev, Jesse Thaler, Energy flow polynomials: A complete linear basis for jet substructure, arXiv:1712.07124 [hep-ph], 2017.

FORMULA

a(n) = A192517(2*n,n) = A192517(m,n) for any m>=2*n. - Max Alekseyev, Oct 18 2017

Euler transform of A076864. - Andrew Howroyd, Oct 23 2019

EXAMPLE

From Gus Wiseman, Jul 18 2018: (Start)

Non-isomorphic representatives of the a(3) = 8 set multipartitions of {1, 1, 2, 2, 3, 3}:

  (123)(123)

  (1)(23)(123)

  (12)(13)(23)

  (1)(1)(23)(23)

  (1)(2)(3)(123)

  (1)(2)(13)(23)

  (1)(1)(2)(3)(23)

  (1)(1)(2)(2)(3)(3)

(End)

MATHEMATICA

seq[n_] := G[2n, x+O[x]^n, {}] // CoefficientList[#, x]&;

seq[15] (* Jean-Fran├žois Alcover, Dec 02 2020, using Andrew Howroyd's code for G in A339065 *)

CROSSREFS

Cf. A001399, A003082, A014395, A014396, A014397, A014398.

Cf. A058389, A050913, A058783, A058390, A058784, A058785, A058391, A058392, A001501, A058528.

Cf. A007716, A007717, A020555, A050535, A076864 (inverse Euler transf.), A076867 (Euler transform) A094574, A316974.

Sequence in context: A116410 A199841 A106606 * A025578 A038151 A230122

Adjacent sequences:  A050532 A050533 A050534 * A050536 A050537 A050538

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Dec 29 1999

EXTENSIONS

More terms from Sean A. Irvine, Oct 02 2011

STATUS

approved

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Last modified January 23 17:47 EST 2021. Contains 340386 sequences. (Running on oeis4.)