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.

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A322137 Number of labeled connected graphs with n edges (the vertices are {1,2,...,k} for some k).

Original entry on oeis.org

1, 1, 3, 17, 140, 1524, 20673, 336259, 6382302, 138525780, 3384988809, 91976158434, 2751122721402, 89833276321440, 3179852538140115, 121287919647418118, 4959343701136929850, 216406753768138678671, 10037782414506891597734, 493175891246093032826160
Offset: 0

Views

Author

Gus Wiseman, Nov 27 2018

Keywords

Crossrefs

Programs

  • Mathematica
    csm[s_]:=With[{c=Select[Tuples[Range[Length[s]],2],And[OrderedQ[#],UnsameQ@@#,Length[Intersection@@s[[#]]]>0]&]},If[c=={},s,csm[Union[Append[Delete[s,List/@c[[1]]],Union@@s[[c[[1]]]]]]]]];
    Table[Length[Select[Subsets[Subsets[Range[n+1],{2}],{n}],And[Union@@#==Range[Max@@Union@@#],Length[csm[#]]==1]&]],{n,6}]
  • PARI
    Connected(v)={my(u=vector(#v));for(n=1, #u, u[n]=v[n] - sum(k=1, n-1, binomial(n-1,k)*v[k]*u[n-k])); u}
    seq(n)={Vec(vecsum(Connected(vector(2*n, j, (1 + x + O(x*x^n))^binomial(j,2)))))} \\ Andrew Howroyd, Nov 28 2018

Extensions

Terms a(8) and beyond from Andrew Howroyd, Nov 28 2018

A053418 Number of unlabeled directed graphs with n arcs and no isolated vertices.

Original entry on oeis.org

1, 1, 5, 17, 80, 365, 1981, 11222, 69511, 455663, 3169244, 23170347, 177513359, 1418920570, 11798710013, 101778754655, 908722427531, 8380602471646, 79692654473866, 780142956502644, 7851084073063731, 81120767066417308
Offset: 0

Views

Author

Vladeta Jovovic, Jan 10 2000

Keywords

Crossrefs

The labeled version is A121252.
Column sums of A350908.
Cf. A000273, A000664, A053454, A053598 (by # of nodes).

Formula

Euler transform of A053454. - Andrew Howroyd, Jan 28 2022

Extensions

Edited and extended by Max Alekseyev, Sep 18 2009

A241706 Number of simple connected graphs on n nodes with diameter 2.

Original entry on oeis.org

0, 0, 1, 4, 14, 59, 373, 4154, 91518, 4116896
Offset: 1

Views

Author

Travis Hoppe and Anna Petrone, Apr 27 2014

Keywords

Crossrefs

Column k=2 of A294522.
Simple connected graphs of diameter k: A241706, A241707, A241708, A241709, A241710.

A201922 Triangle read by rows: T(n,m) = number of unlabeled graphs on n nodes with m connected components, m = 1,2,...,n.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 6, 3, 1, 1, 21, 8, 3, 1, 1, 112, 30, 9, 3, 1, 1, 853, 145, 32, 9, 3, 1, 1, 11117, 1028, 154, 33, 9, 3, 1, 1, 261080, 12320, 1065, 156, 33, 9, 3, 1, 1, 11716571, 274806, 12513, 1074, 157, 33, 9, 3, 1, 1, 1006700565, 12007355, 276114, 12550, 1076, 157, 33, 9, 3, 1, 1
Offset: 1

Views

Author

Max Alekseyev, Dec 06 2011

Keywords

Examples

			Triangle starts:
    1
    1   1
    2   1   1
    6   3   1   1
   21   8   3   1   1
  112  30   9   3   1   1
  853 145  32   9   3   1   1 ...
		

Crossrefs

Cf. A001349 (first column), A000088 (row sum), A201968 (limits in the diagonals), A106240, A274934 (2nd column).

Programs

  • Mathematica
    nn=10; c=(A000088=Table[NumberOfGraphs[n], {n,0,nn}]; f[x_] = 1-Product[1/(1-x^k)^a[k], {k,1,nn}]; a[0]=a[1]=a[2]=1; coes=CoefficientList[Series[f[x], {x,0,nn}], x]; sol=First[Solve[Thread[Rest[coes+A000088]==0]]]; Table[a[n], {n,0,nn}]/.sol); f[list_]:=Select[list,#>0&]; g=Product[1/(1-y x^n)^c[[n+1]], {n,1,nn}]; Map[f, Drop[CoefficientList[Series[g, {x,0,nn}], {x,y}],1]] //Flatten (* Geoffrey Critzer, Apr 19 2012  (c in above Mma code is given by Jean Francois Alcover in A001349) *)

Formula

T(n,m) = sum over the partitions of n with m parts: 1*K1 + 2*K2 + ... + n*Kn = n, K1 + K2 + ... + Kn = m, of Product_{i=1..n} binomial(A001349(i) + Ki - 1, Ki).
O.g.f.: Product_{n>=1} 1/(1 - y*x^n)^A001349(n). - Geoffrey Critzer, Apr 19 2012

A241707 Number of simple connected graphs on n nodes with diameter 3.

Original entry on oeis.org

0, 0, 0, 1, 5, 43, 387, 5797, 148229, 6959721
Offset: 1

Views

Author

Travis Hoppe and Anna Petrone, Apr 27 2014

Keywords

Crossrefs

Column k=3 of A294522.
Simple connected graphs of diameter k: A241706, A241707, A241708, A241709, A241710.

A263859 Triangle read by rows: T(n,k) (n>=1, k>=0) is the number of posets with n elements and rank k (or depth k+1).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 8, 6, 1, 1, 20, 31, 10, 1, 1, 55, 162, 84, 15, 1, 1, 163, 940, 734, 185, 21, 1, 1, 556, 6372, 7305, 2380, 356, 28, 1, 1, 2222, 52336, 86683, 35070, 6259, 623, 36, 1, 1, 10765, 534741, 1261371, 619489, 125597, 14258, 1016, 45, 1
Offset: 1

Views

Author

Christian Stump, Oct 28 2015

Keywords

Comments

Row sums give A000112, n >= 1.
The rank of a poset is the number of cover relations in a maximal chain.

Examples

			Triangle begins:
1,
1,1,
1,3,1,
1,8,6,1,
1,20,31,10,1,
1,55,162,84,15,1,
1,163,940,734,185,21,1,
1,556,6372,7305,2380,356,28,1,
1,2222,52336,86683,35070,6259,623,36,1,
1,10765,534741,1261371,619489,125597,14258,1016,45,1,
...
		

Crossrefs

Cf. A000112 (row sums), A342500 (connected).

Extensions

More terms from Brinkmann-McKay (2002) added by N. J. A. Sloane, Mar 18 2017

A303832 The number of edge-rooted unlabeled connected graphs with n edges.

Original entry on oeis.org

1, 1, 4, 10, 32, 101, 346, 1220, 4517, 17338, 69107, 285009, 1215015, 5344224, 24223641, 113001129, 541913075, 2668817544, 13484234188, 69831773559, 370361639587, 2009988998148, 11153858854425, 63242354288220, 366140089188603, 2163036956456422, 13031489297543608
Offset: 1

Views

Author

R. J. Mathar, May 04 2018

Keywords

Examples

			a(1)=1: the connected graph with 1 edge (which is rooted).
a(2)=1: the connected graph with 2 edges (one rooted).
a(3)=4: the triangle graph with one choice of rooting, the linear tree with either the middle or a terminating edge rooted, the star graph with one edge rooted.
		

Crossrefs

Cf. A126133 (not necessarily connected), A000664, A303830 (by number of nodes).

Programs

  • PARI
    \\ See A339063 for G.
    seq(n)={my(A=O(x*x^n)); Vec((G(2*n, x+A, [1, 1]) + G(2*n, x+A, [2]))/(2*G(2*n, x+A, [])*(1+x)))} \\ Andrew Howroyd, Nov 21 2020

Formula

G.f. A(x) satisfies: A(x)*A000664(x) = A126133(x).

A322147 Regular triangle read by rows where T(n,k) is the number of labeled connected graphs with loops with n edges and k vertices, 1 <= k <= n+1.

Original entry on oeis.org

1, 1, 1, 0, 2, 3, 0, 1, 10, 16, 0, 0, 12, 79, 125, 0, 0, 6, 162, 847, 1296, 0, 0, 1, 179, 2565, 11436, 16807, 0, 0, 0, 116, 4615, 47100, 185944, 262144, 0, 0, 0, 45, 5540, 121185, 987567, 3533720, 4782969, 0, 0, 0, 10, 4720, 220075, 3376450, 23315936, 76826061, 100000000
Offset: 0

Views

Author

Gus Wiseman, Nov 28 2018

Keywords

Examples

			Triangle begins:
  1
  1     1
  0     2     3
  0     1    10    16
  0     0    12    79   125
  0     0     6   162   847  1296
  0     0     1   179  2565 11436 16807
		

Crossrefs

Row sums are A322151. Last column is A000272.
Column sums are A062740.

Programs

  • Mathematica
    multsubs[set_,k_]:=If[k==0,{{}},Join@@Table[Prepend[#,set[[i]]]&/@multsubs[Drop[set,i-1],k-1],{i,Length[set]}]];
    csm[s_]:=With[{c=Select[Tuples[Range[Length[s]],2],And[OrderedQ[#],UnsameQ@@#,Length[Intersection@@s[[#]]]>0]&]},If[c=={},s,csm[Union[Append[Delete[s,List/@c[[1]]],Union@@s[[c[[1]]]]]]]]];
    Table[If[n==0,1,Length[Select[Subsets[multsubs[Range[k],2],{n}],And[Union@@#==Range[k],Length[csm[#]]==1]&]]],{n,0,6},{k,1,n+1}]
  • PARI
    Connected(v)={my(u=vector(#v)); for(n=1, #u, u[n]=v[n] - sum(k=1, n-1, binomial(n-1, k)*v[k]*u[n-k])); u}
    M(n)={Mat([Col(p, -(n+1)) | p<-Connected(vector(2*n, j, (1 + x + O(x*x^n) )^binomial(j+1,2)))[1..n+1]])}
    { my(T=M(10)); for(n=1, #T, print(T[n,][1..n])) } \\ Andrew Howroyd, Nov 29 2018

Extensions

Terms a(28) and beyond from Andrew Howroyd, Nov 29 2018

A322151 Number of labeled connected graphs with loops with n edges (the vertices are {1,2,...,k} for some k).

Original entry on oeis.org

1, 2, 5, 27, 216, 2311, 30988, 499919, 9431026, 203743252, 4960335470, 134382267082, 4009794148101, 130668970606412, 4617468180528235, 175867725701333896, 7182126650899080024, 313063334893103361130, 14507460736615554141354, 712192629608088061633746
Offset: 0

Views

Author

Gus Wiseman, Nov 28 2018

Keywords

Crossrefs

Row sums of A322147. The unlabeled version is A191970.

Programs

  • Mathematica
    multsubs[set_,k_]:=If[k==0,{{}},Join@@Table[Prepend[#,set[[i]]]&/@multsubs[Drop[set,i-1],k-1],{i,Length[set]}]];
    csm[s_]:=With[{c=Select[Tuples[Range[Length[s]],2],And[OrderedQ[#],UnsameQ@@#,Length[Intersection@@s[[#]]]>0]&]},If[c=={},s,csm[Union[Append[Delete[s,List/@c[[1]]],Union@@s[[c[[1]]]]]]]]];
    Table[Length[Select[Subsets[multsubs[Range[n+1],2],{n}],And[Union@@#==Range[Max@@Union@@#],Length[csm[#]]==1]&]],{n,5}]
  • PARI
    Connected(v)={my(u=vector(#v)); for(n=1, #u, u[n]=v[n] - sum(k=1, n-1, binomial(n-1, k)*v[k]*u[n-k])); u}
    seq(n)={Vec(vecsum(Connected(vector(2*n, j, (1 + x + O(x*x^n))^binomial(j+1,2)))))} \\ Andrew Howroyd, Nov 28 2018

Extensions

Terms a(7) and beyond from Andrew Howroyd, Nov 28 2018

A339040 Number of unlabeled connected simple graphs with n edges rooted at two noninterchangeable vertices.

Original entry on oeis.org

1, 3, 10, 35, 125, 460, 1747, 6830, 27502, 113987, 485971, 2129956, 9591009, 44341610, 210345962, 1023182861, 5100235807, 26035673051, 136023990102, 726877123975, 3970461069738, 22156281667277, 126234185382902, 733899631974167, 4351500789211840
Offset: 1

Views

Author

Andrew Howroyd, Nov 20 2020

Keywords

Crossrefs

Programs

  • PARI
    \\ See A339063 for G.
    seq(n)={my(A=O(x*x^n), g=G(2*n, x+A, [])); Vec(G(2*n, x+A, [1, 1])/g - (G(2*n, x+A, [1])/g)^2)}

Formula

G.f.: f(x)/g(x) - r(x)^2 where f(x), g(x) and r(x) are the g.f.'s of A339063, A000664 and A339039.
Previous Showing 41-50 of 74 results. Next