A050535 -id:A050535 - cp's OEIS frontend

A191970 Number of connected graphs with n edges with loops allowed.

1, 2, 2, 6, 12, 33, 93, 287, 940, 3309, 12183, 47133, 190061, 796405, 3456405, 15501183, 71681170, 341209173, 1669411182, 8384579797, 43180474608, 227797465130, 1229915324579, 6790642656907, 38311482445514, 220712337683628, 1297542216770482, 7779452884747298

Offset: 0

Alberto Tacchella, Jun 20 2011

nonn

Inverse Euler transform of A053419.
From R. J. Mathar, Jul 25 2017: (Start)
The Multiset Transform gives the number of graphs with n edges (loops allowed) and k components (0<=k<=n):
 1
2
2 3
6 4 4
12 15 6 5
33 36 24 8 6
93 111 64 33 10 7
287 324 207 92 42 12 8
940 1036 633 308 120 51 14 9
3309 3408 2084 966 409 148 60 16 10
12183 11897 6959 3243 1305 510 176 69 18 11
47133 43137 24415 10970 4432 1644 611 204 78 20 12
190061 163608 88402 38763 15125 5628 1983 712 232 87 22 13
796405 644905 332979 140671 53732 19316 6824 2322 813 260 96 24 14
3456405 2639871 1299054 529179 195517 68878 23515 8020 2661 914 288 105 26 15 (End)

			a(1)=2: Either one node with the edge equal to a loop, or two nodes connected by the edge. a(2)=2: Either three nodes on a chain connected by the two edges, or two nodes connected by an edge, one node with a loop. Apparently multi-loops are not allowed (?). - _R. J. Mathar_, Jul 25 2017

Andrew Howroyd, Table of n, a(n) for n = 0..50
Gus Wiseman, Non-isomorphic representatives of the a(1) = 1 through a(4) = 12 connected graphs with loops.

Row sums of A322114.

Cf. A000664, A002905, A007718, A050535, A053419, A054923, A191646, A191970, A275421, A322133, A322151, A322152.

\\ See A322114 for InvEulerMT, G.
seq(n)={vecsum([Vec(p+O(y^n), -n) | p<-InvEulerMT(vector(n, k, G(k, y + O(y^n))))])} \\ Andrew Howroyd, Oct 22 2019

Terms a(25) and beyond from Andrew Howroyd, Oct 22 2019

A316974 Number of non-isomorphic strict multiset partitions of {1, 1, 2, 2, 3, 3, ..., n, n}.

Original entry on oeis.org

1, 1, 4, 14, 49, 173, 652, 2494

Offset: 0

Gus Wiseman, Jul 17 2018

Also the number of unlabeled multigraphs with n edges, allowing loops, spanning an initial interval of positive integers with no equivalent vertices (two vertices are equivalent if in every edge the multiplicity of the first is equal to the multiplicity of the second). For example, non-isomorphic representatives of the a(2) = 4 multigraphs are {(1,2),(1,3)}, {(1,1),(1,2)}, {(1,1),(2,2)}, {(1,1),(1,1)}.

			Non-isomorphic representatives of the a(3) = 14 strict multiset partitions:
  (112233),
  (1)(12233), (11)(2233), (12)(1233), (112)(233),
  (1)(2)(1233), (1)(12)(233), (1)(23)(123), (2)(11)(233), (11)(22)(33), (12)(13)(23),
  (1)(2)(3)(123), (1)(2)(12)(33), (1)(2)(13)(23).

Cf. A001055, A007716, A007717, A007719, A020554, A020555, A045778, A050535, A053419, A061742, A094574, A162247, A316892, A316972.

a(7) from Andrew Howroyd, Feb 07 2020

A020554 Number of multigraphs on n labeled edges (without loops).

Original entry on oeis.org

1, 1, 3, 16, 139, 1750, 29388, 624889, 16255738, 504717929, 18353177160, 769917601384, 36803030137203, 1984024379014193, 119571835094300406, 7995677265437541258, 589356399302126773920, 47609742627231823142029, 4193665147256300117666879

Offset: 0

Gilbert Labelle (gilbert(AT)lacim.uqam.ca) and Simon Plouffe

Or, number of bicoverings of an n-set.
Or, number of 2-covers of [1,...,n].
Also the number of set multipartitions (multisets of sets) of {1, 1, 2, 2, 3, 3, ..., n, n}. - Gus Wiseman, Jul 18 2018

			From _Gus Wiseman_, Jul 18 2018: (Start)
The a(3) = 16 set multipartitions of {1, 1, 2, 2, 3, 3}:
  (123)(123)
  (1)(23)(123) (2)(13)(123) (3)(12)(123) (12)(13)(23)
  (1)(1)(23)(23) (1)(2)(3)(123) (1)(2)(13)(23) (1)(3)(12)(23) (2)(2)(13)(13) (2)(3)(12)(13) (3)(3)(12)(12)
  (1)(1)(2)(3)(23) (1)(2)(2)(3)(13) (1)(2)(3)(3)(12)
  (1)(1)(2)(2)(3)(3)
(End)

G. Paquin, Dénombrement de multigraphes enrichis, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004.

Alois P. Heinz, Table of n, a(n) for n = 0..100
Peter Cameron, Thomas Prellberg, and Dudley Stark, Asymptotic enumeration of 2-covers and line graphs, Discrete Math. 310 (2010), no. 2, 230-240 (see s_n).
L. Comtet, Birecouvrements et birevêtements d'un ensemble fini, Studia Sci. Math. Hungar 3 (1968): 137-152. [Annotated scanned copy. Warning: the table of v(n,k) has errors.]
G. Labelle, Counting enriched multigraphs according to the number of their edges (or arcs), Discrete Math., 217 (2000), 237-248.
G. Paquin, Dénombrement de multigraphes enrichis, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004. [Cached copy, with permission]

Row 2 of A188392.

Cf. A002718, A007716, A020555, A050535, A094574, A316974.

Ceiling[ CoefficientList[ Series[ Exp[ -1 + (Exp[ z ] - 1)/2 ]Sum[ Exp[ s(s - 1)z/2 ]/s!, {s, 0, 21} ], {z, 0, 9} ], z ] Table[ n!, {n, 0, 9} ] ] (* Mitch Harris, May 01 2004 *)
sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
Table[Length[Select[mps[Ceiling[Range[1/2,n,1/2]]],And@@UnsameQ@@@#&]],{n,5}] (* Gus Wiseman, Jul 18 2018 *)

E.g.f.: exp(-3/2+exp(x)/2) * Sum_{n>=0} exp(binomial(n, 2)*x)/n! [Comtet]. - Vladeta Jovovic, Apr 27 2004
E.g.f. (an equivalent version in Maple format): G:=exp(-1+(exp(z)-1)/2)*sum(exp(s*(s-1)*z/2)/s!, s=0..infinity);
E.g.f.: exp((exp(x)-1)/2)*Sum_{n>=0} A020556(n)*(x/2)^n/n!. - Vladeta Jovovic, May 02 2004
Stirling_2 transform of A014500.
The e.g.f.'s of A020554 (S(x)) and A014500 (U(x)) are related by S(x) = U(e^x-1).

A192517 Table read by antidiagonals: T(n,k) = number of multigraphs with n vertices and k edges, with no loops allowed (n >= 1, k >= 0).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 1, 0, 1, 1, 3, 3, 1, 0, 1, 1, 3, 6, 4, 1, 0, 1, 1, 3, 7, 11, 5, 1, 0, 1, 1, 3, 8, 17, 18, 7, 1, 0, 1, 1, 3, 8, 21, 35, 32, 8, 1, 0, 1, 1, 3, 8, 22, 52, 76, 48, 10, 1, 0, 1, 1, 3, 8, 23, 60, 132, 149, 75, 12, 1, 0

Offset: 1

Alberto Tacchella, Jul 03 2011

Rows converge to sequence A050535, i.e. T(n,k) = A050535(k) for n >= 2k.

			Table begins:
[1,0,0,0,0,0,0,0,0,...],
[1,1,1,1,1,1,1,1,1,...],
[1,1,2,3,4,5,7,8,10,...],
[1,1,3,6,11,18,32,48,75,...],
[1,1,3,7,17,35,76,149,291,...],
[1,1,3,8,21,52,132,313,741,...],
[1,1,3,8,22,60,173,471,1303,...],
[1,1,3,8,23,64,197,588,1806,...],
...

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 171.

Andrew Howroyd, Table of n, a(n) for n = 1..1275 (terms 1..78 from Alberto Tacchella computed using nauty 2.4, terms 79..595 from Sean A. Irvine computed using cycle index method of Harary and Palmer).
R. J. Mathar, Statistics on Small Graphs, arXiv:1709.09000 [math.CO] (2017), Table 69.

Cf. A008406, A191646, A003082 (row 4), A014395 (row 5), A014396 (row 6).

\\ See A191646 for G function.
R(n)={Mat(vectorv(n, k, concat([1], G(k, n-1))))}
{ my(A=R(10)); for(n=1, #A, for(k=1, #A, print1(A[n,k], ", "));print) } \\ Andrew Howroyd, May 14 2018

A331461 Array read by antidiagonals: A(n,k) is the number of nonequivalent binary matrices with k columns and any number of nonzero rows with n ones in every column up to permutation of rows and columns.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 3, 1, 1, 1, 5, 8, 4, 1, 1, 1, 7, 23, 16, 5, 1, 1, 1, 11, 66, 93, 30, 6, 1, 1, 1, 15, 212, 652, 332, 50, 7, 1, 1, 1, 22, 686, 6369, 6414, 1062, 80, 8, 1, 1, 1, 30, 2389, 79568, 226041, 56712, 3117, 120, 9, 1, 1, 1, 42, 8682, 1256425, 12848128, 7295812, 441881, 8399, 175, 10, 1, 1

Offset: 0

Andrew Howroyd, Jan 18 2020

A(n,k) is the number of non-isomorphic set multipartitions (multiset of sets) with k parts each part has size n.

			Array begins:
===========================================================
n\k | 0 1 2   3    4       5          6              7
----+-----------------------------------------------------
  0 | 1 1 1   1    1       1          1              1 ...
  1 | 1 1 2   3    5       7         11             15 ...
  2 | 1 1 3   8   23      66        212            686 ...
  3 | 1 1 4  16   93     652       6369          79568 ...
  4 | 1 1 5  30  332    6414     226041       12848128 ...
  5 | 1 1 6  50 1062   56712    7295812     1817321457 ...
  6 | 1 1 7  80 3117  441881  195486906   200065951078 ...
  7 | 1 1 8 120 8399 3006771 4298181107 17131523059493 ...
  ...
The A(2,3) = 8 matrices are:
  [1 0 0]  [1 1 0]  [1 1 1]  [1 1 0]  [1 1 0]  [1 1 1]  [1 1 0]  [1 1 1]
  [1 0 0]  [1 0 0]  [1 0 0]  [1 1 0]  [1 0 1]  [1 1 0]  [1 0 1]  [1 1 1]
  [0 1 0]  [0 1 0]  [0 1 0]  [0 0 1]  [0 1 0]  [0 0 1]  [0 1 1]
  [0 1 0]  [0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]
  [0 0 1]  [0 0 1]
  [0 0 1]

Andrew Howroyd, Table of n, a(n) for n = 0..152

Rows n=0..6 are A000012, A000041, A050535, A050913, A058783, A058784, A058785.
Columns k=0..4 are A000012, A000012, A000027(n+1), A002624, A331720.
Cf. A188392, A262809, A304942, A306018, A330942, A331485, A331508, A331509, A331510.

\\ See A304942 for Blocks
T(n,k)={Blocks(k, n*k, n)}
{ for(n=0, 7, for(k=0, 6, print1(T(n,k), ", ")); print) }

A306018(n) = Sum_{d|n} A(n/d, d).

A339065 Number of unlabeled loopless multigraphs with n edges rooted at two noninterchangeable vertices.

Original entry on oeis.org

1, 4, 17, 69, 281, 1147, 4784, 20345, 88726, 396971, 1823920, 8605364, 41684417, 207201343, 1056244832, 5518054182, 29521703655, 161625956908, 904857279576, 5176569819167, 30241443710950, 180293374961036, 1096240011165724, 6793998104717138, 42894087222036022, 275735424352928682

Offset: 0

Andrew Howroyd, Nov 22 2020

nonn

			The a(1) = 4 cases correspond to a single edge which can be attached to zero, one or both of the roots.

Cf. A050535, A007717 (one root), A339042, A339063, A339066.

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_, t_] := Product[With[{g = GCD[v[[i]], v[[j]]]}, t[v[[i]]*v[[j]]/ g]^g], {i, 2, Length[v]}, {j, 1, i - 1}]*Product[With[{c = v[[i]]}, t[c]^Quotient[c-1, 2]*If[OddQ[c], 1, t[c/2]]], {i, 1, Length[v]}];
G[n_, x_, r_] := Module[{s = 0}, Do[s += permcount[p]*edges[Join[r, p], 1/(1 - x^#) &], {p, IntegerPartitions[n]}]; s/n!];
seq[n_] := Module[{A = O[x]^n}, G[2n, x+A, {1, 1}]//CoefficientList[#, x]&];
seq[15] (* Jean-François Alcover, Dec 01 2020, after Andrew Howroyd *)

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, t) = {prod(i=2, #v, prod(j=1, i-1, my(g=gcd(v[i], v[j])); t(v[i]*v[j]/g)^g )) * prod(i=1, #v, my(c=v[i]); t(c)^((c-1)\2)*if(c%2, 1, t(c/2)))}
G(n, x, r)={my(s=0); forpart(p=n, s+=permcount(p)*edges(concat(r, Vec(p)), i->1/(1-x^i))); s/n!}
seq(n)={my(A=O(x*x^n)); Vec((G(2*n, x+A, [1, 1])))}

A007719 Number of independent polynomial invariants of symmetric matrix of order n.

Original entry on oeis.org

1, 2, 4, 11, 30, 95, 328, 1211, 4779, 19902, 86682, 393072, 1847264, 8965027, 44814034, 230232789, 1213534723, 6552995689, 36207886517, 204499421849, 1179555353219, 6942908667578, 41673453738272, 254918441681030, 1588256152307002, 10073760672179505

Offset: 0

Colin Mallows

Also, number of connected multigraphs with n edges (allowing loops) and any number of nodes.

Also the number of non-isomorphic connected multiset partitions of {1, 1, 2, 2, 3, 3, ..., n, n}. - Gus Wiseman, Jul 18 2018

			From _Gus Wiseman_, Jul 18 2018: (Start)
Non-isomorphic representatives of the a(3) = 11 connected multiset partitions of {1, 1, 2, 2, 3, 3}:
  (112233),
  (1)(12233), (12)(1233), (112)(233), (123)(123),
  (1)(2)(1233), (1)(12)(233), (1)(23)(123), (12)(13)(23),
  (1)(2)(3)(123), (1)(2)(13)(23).
(End)

Andrew Howroyd, Table of n, a(n) for n = 0..50
R. J. Mathar, Statistics on Small Graphs, arXiv:1709.09000 [math.CO] (2017) Table 63.

Row sums of A322115.

Cf. A002905, A007716, A007717, A007719, A020555, A050535, A053419, A076864, A191970, A316972, A316974.

mob[m_, n_] := If[Mod[m, n] == 0, MoebiusMu[m/n], 0];
EULERi[b_] := Module[{a, c, i, d}, c = {}; For[i = 1, i <= Length[b], i++,
  c = Append[c, i*b[[i]] - Sum[c[[d]]*b[[i - d]], {d, 1, i - 1}]]]; a = {};
  For[i = 1, i <= Length[b], i++, a = Append[a, (1/i)*Sum[mob[i, d]*c[[d]], {d, 1, i}]]]; Return[a]];
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];
Kq[q_, t_, k_] := SeriesCoefficient[1/Product[g = GCD[t, q[[j]]]; (1 - x^(q[[j]]/g))^g, {j, 1, Length[q]}], {x, 0, k}];
RowSumMats[n_, m_, k_] := Module[{s = 0}, Do[s += permcount[q]* SeriesCoefficient[ Exp[Sum[Kq[q, t, k]/t x^t, {t, 1, n}]], {x, 0, n}], {q, IntegerPartitions[m]}]; s/m!];
A007717 = Table[Print[n]; RowSumMats[n, 2 n, 2], {n, 0, 20}];
Join[{1}, EULERi[Rest[A007717]]] (* Jean-François Alcover, Oct 29 2018, using Andrew Howroyd's code for A007717 *)

Inverse Euler transform of A007717.

a(0)=1 added by Alberto Tacchella, Jun 20 2011

a(7)-a(25) from Franklin T. Adams-Watters, Jun 21 2011

A053419 Number of graphs with loops (symmetric relations) with n edges.

Original entry on oeis.org

1, 2, 5, 14, 38, 107, 318, 972, 3111, 10410, 36371, 132656, 504636, 1998361, 8224448, 35112342, 155211522, 709123787, 3342875421, 16234342515, 81102926848, 416244824068, 2192018373522, 11831511359378, 65387590986455, 369661585869273, 2135966349269550, 12604385044890628

Offset: 0

Vladeta Jovovic, Jan 10 2000

nonn

In a multiset partition, two vertices are equivalent if in every block the multiplicity of the first is equal to the multiplicity of the second. a(n) is the number of non-isomorphic multiset partitions of {1, 1, 2, 2, 3, 3, ..., n, n} with no equivalent vertices. For example, non-isomorphic representatives of the a(2) = 5 multiset partitions are (1)(122), (11)(22), (1)(1)(22), (1)(2)(12), (1)(1)(2)(2). - Gus Wiseman, Jul 18 2018

a(n) is the number of unlabeled simple graphs with n edges rooted at one vertex. - Andrew Howroyd, Nov 22 2020

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

Cf. A000664, A000666, A007716, A007717, A020555, A050535, A053419, A094574, A191970 (multisets), A316974, A339063.

seq[n_] := Module[{A = O[x]^n}, G[2n, x+A, {1}] // CoefficientList[#, x]&]; (* Jean-François Alcover, Dec 03 2020, using Andrew Howroyd's code for g.f. G in A339063 *)

\\ See A339063 for G.
seq(n)={my(A=O(x*x^n)); Vec(G(2*n, x+A, [1]))} \\ Andrew Howroyd, Nov 22 2020

Euler transform of A191970. - Andrew Howroyd, Oct 22 2019

a(16)-a(24) from Max Alekseyev, Jan 22 2010

Terms a(25) and beyond from Andrew Howroyd, Oct 22 2019

A058783 Number of n-rowed binary matrices with all row sums 4, up to row and column permutation; bipartite graphs with all nodes of degree 4 in a distinguished bipartite n-block, up to isomorphism.

Original entry on oeis.org

1, 1, 5, 30, 332, 6414, 226041, 12848128, 1064292052, 119252205304, 17239075745190, 3113843614322530, 686491853010870156, 181386885029173595218, 56595769613704915215101, 20597536264356706999502705, 8652615103513713632218678155, 4157673185369121151936091009448

Offset: 0

Vladeta Jovovic, Nov 28 2000

nonn

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

Row n=4 of A331461.

Cf. A050535, A050913, A058784, A058785.

Terms a(8)-a(17) from Max Alekseyev, May 04 2018

A321760 Number of non-isomorphic multiset partitions of weight n with no constant parts or vertices that appear in only one part.

Original entry on oeis.org

1, 0, 0, 0, 1, 1, 7, 9, 37, 79, 273, 755, 2648, 8432, 29872, 104624, 384759, 1432655, 5502563, 21533141, 86291313, 352654980, 1471073073, 6253397866, 27083003687, 119399628021, 535591458635, 2443030798539, 11326169401988, 53343974825122, 255121588496338

Offset: 0

Gus Wiseman, Nov 29 2018

nonn

Also the number of nonnegative integer matrices up to row and column permutations with sum of elements equal to n in which every row and column has at least two nonzero entries.

The weight of a multiset partition is the sum of sizes of its parts. Weight is generally not the same as number of vertices.

			Non-isomorphic representatives of the a(4) = 1 through a(7) = 9 multiset partitions:
  {{1,2},{1,2}}  {{1,2},{1,2,2}}  {{1,1,2},{1,2,2}}    {{1,1,2},{1,2,2,2}}
                                  {{1,2},{1,1,2,2}}    {{1,2},{1,1,2,2,2}}
                                  {{1,2},{1,2,2,2}}    {{1,2},{1,2,2,2,2}}
                                  {{1,2,2},{1,2,2}}    {{1,2,2},{1,1,2,2}}
                                  {{1,2,3},{1,2,3}}    {{1,2,2},{1,2,2,2}}
                                  {{1,2},{1,2},{1,2}}  {{1,2,3},{1,2,3,3}}
                                  {{1,2},{1,3},{2,3}}  {{1,2},{1,2},{1,2,2}}
                                                       {{1,2},{1,3},{2,3,3}}
                                                       {{1,3},{2,3},{1,2,3}}

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

Row sums of A369286.

Cf. A001970, A007716, A050535, A055884, A120733, A317533, A320665, A320798, A320801, A320808, A321407.

Vec(G(20,1)) \\ G defined in A369286. - Andrew Howroyd, Jan 28 2024

a(11) onwards from Andrew Howroyd, Jan 27 2024

cp's OEIS Frontend

A191970 Number of connected graphs with n edges with loops allowed.

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A316974 Number of non-isomorphic strict multiset partitions of {1, 1, 2, 2, 3, 3, ..., n, n}.

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A020554 Number of multigraphs on n labeled edges (without loops).

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A192517 Table read by antidiagonals: T(n,k) = number of multigraphs with n vertices and k edges, with no loops allowed (n >= 1, k >= 0).

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A331461 Array read by antidiagonals: A(n,k) is the number of nonequivalent binary matrices with k columns and any number of nonzero rows with n ones in every column up to permutation of rows and columns.

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A339065 Number of unlabeled loopless multigraphs with n edges rooted at two noninterchangeable vertices.

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A007719 Number of independent polynomial invariants of symmetric matrix of order n.

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A053419 Number of graphs with loops (symmetric relations) with n edges.

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