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.

Previous Showing 31-40 of 44 results. Next

A101389 Number of n-vertex unlabeled oriented graphs without endpoints.

Original entry on oeis.org

1, 1, 1, 3, 21, 369, 16929, 1913682, 546626268, 406959998851, 808598348346150, 4358157210587930509, 64443771774627635711718, 2636248889492487709302815665, 300297332862557660078111708007894, 95764277032243987785712142452776403618, 85885545190811866954428990373255822969983915
Offset: 0

Views

Author

Goran Kilibarda, Vladeta Jovovic, Jan 14 2005

Keywords

Examples

			a(3) = 3 because there are 2 distinct orientations of the triangle K_3 plus the empty graph on 3 vertices.
		

Crossrefs

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    oedges(v) = {sum(i=2, #v, sum(j=1, i-1, gcd(v[i], v[j]))) + sum(i=1, #v, (v[i]-1)\2)}
    ographsCycleIndex(n)={my(s=0); forpart(p=n, s+=permcount(p) * 3^oedges(p) * sMonomial(p)); s/n!}
    ographs(n)={sum(k=0, n, ographsCycleIndex(k)*x^k) + O(x*x^n)}
    trees(n,k)={sRevert(x*sv(1)/sExp(k*x*sv(1) + O(x^n)))}
    cycleIndexSeries(n)={my(g=ographs(n), tr=trees(n,2), tu=tr-tr^2); sSolve( g/sExp(tu), tr )*symGroupSeries(n)}
    NumUnlabeledObjsSeq(cycleIndexSeries(15)) \\ Andrew Howroyd, Dec 27 2020
    
  • PARI
    \\ faster stand-alone version
    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]-1)\2)}
    seq(n)={Vec(sum(k=0, n, my(s=0); forpart(p=k, s+=permcount(p) * 3^edges(p) * prod(i=1, #p, my(d=p[i]); (1-x^d)^2 + O(x*x^(n-k))) ); x^k*s/k!)/(1-x^2))} \\ Andrew Howroyd, Jan 22 2021

Extensions

a(0)=1 prepended and terms a(9) and beyond from Andrew Howroyd, Dec 27 2020

A304485 Regular triangle where T(n,k) is the number of inequivalent colorings of free pure symmetric multifunctions (with empty expressions allowed) with n positions and k leaves.

Original entry on oeis.org

1, 1, 0, 1, 2, 0, 1, 6, 4, 0, 1, 12, 23, 7, 0, 1, 20, 81, 73, 12, 0, 1, 30, 209, 407, 206, 19, 0, 1, 42, 451, 1566, 1751, 534, 30, 0, 1, 56, 858, 4711, 9593, 6695, 1299, 45, 0, 1, 72, 1494, 11951, 39255, 51111, 23530, 3004, 67, 0, 1, 90, 2430, 26752, 130220, 278570, 245319, 77205, 6664, 97, 0
Offset: 1

Views

Author

Gus Wiseman, Aug 17 2018

Keywords

Comments

A free pure symmetric multifunction (with empty expressions allowed) f in EOME is either (case 1) a positive integer, or (case 2) a possibly empty expression of the form h[g_1, ..., g_k] where k >= 0, h is in EOME, each of the g_i for i = 1, ..., k is in EOME, and for i < j we have g_i <= g_j under a canonical total ordering of EOME, such as the Mathematica ordering of expressions.
T(n,k) is also the number of inequivalent colorings of orderless Mathematica expressions with n positions and k leaves.

Examples

			Inequivalent representatives of the T(5,3) = 23 Mathematica expressions:
  1[][1,1]  1[1,1][]  1[1][1]  1[1[1]]  1[1,1[]]
  1[][1,2]  1[1,2][]  1[1][2]  1[1[2]]  1[1,2[]]
  1[][2,2]  1[2,2][]  1[2][1]  1[2[1]]  1[2,1[]]
  1[][2,3]  1[2,3][]  1[2][2]  1[2[2]]  1[2,2[]]
                      1[2][3]  1[2[3]]  1[2,3[]]
Triangle begins:
    1
    1    0
    1    2    0
    1    6    4    0
    1   12   23    7    0
    1   20   81   73   12    0
    1   30  209  407  206   19    0
    1   42  451 1566 1751  534   30    0
		

Crossrefs

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    cycleIndexSeries(n)={my(p=O(x)); for(n=1, n, p = x*sv(1) + x*p*sExp(p)); p}
    T(n)={my(v=Vec(InequivalentColoringsSeq(sFuncSubst(cycleIndexSeries(n), i->sv(i)*y^i)))); vector(n, n, Vecrev(v[n]/y, n))}
    { my(A=T(10)); for(n=1, #A, print(A[n])) } \\ Andrew Howroyd, Jan 01 2021

Extensions

Terms a(37) and beyond from Andrew Howroyd, Jan 01 2021

A330473 Regular triangle where T(n,k) is the number of non-isomorphic multiset partitions of k-element multiset partitions of multisets of size n.

Original entry on oeis.org

1, 0, 1, 0, 2, 4, 0, 3, 8, 10, 0, 5, 28, 38, 33, 0, 7, 56, 146, 152, 91, 0, 11, 138, 474, 786, 628, 298, 0, 15, 268, 1388, 3117, 3808, 2486, 910, 0, 22, 570, 3843, 11830, 19147, 18395, 9986, 3017, 0, 30, 1072, 10094, 40438, 87081, 110164, 86388, 39889, 9945
Offset: 0

Views

Author

Gus Wiseman, Dec 20 2019

Keywords

Comments

As an alternative description, T(n,k) is the number of non-isomorphic multisets of nonempty multisets of nonempty multisets with n leaves whose multiset union consists of k multisets.

Examples

			Triangle begins:
   1
   0   1
   0   2   4
   0   3   8  10
   0   5  28  38  33
   0   7  56 146 152  91
   0  11 138 474 786 628 298
For example, row n = 3 counts the following multiset partitions:
  {{111}}  {{1}{11}}    {{1}{1}{1}}
  {{112}}  {{1}{12}}    {{1}{1}{2}}
  {{123}}  {{1}{23}}    {{1}{2}{3}}
           {{2}{11}}    {{1}}{{1}{1}}
           {{1}}{{11}}  {{1}}{{1}{2}}
           {{1}}{{12}}  {{1}}{{2}{3}}
           {{1}}{{23}}  {{2}}{{1}{1}}
           {{2}}{{11}}  {{1}}{{1}}{{1}}
                        {{1}}{{1}}{{2}}
                        {{1}}{{2}}{{3}}
		

Crossrefs

Row sums are A318566.
Column k = 1 is A000041 (for n > 0).
Column k = n is A007716.
Partitions of partitions of partitions are A007713.
Twice-factorizations are A050336.
The 2-dimensional version is A317533.
See A330472 for a variation.

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    ColGf(k, n)={my(A=symGroupSeries(n)); OgfSeries(sCartProd(sExp(A), sSubstOp(polcoef(sExp(A), k, x)*x^k + O(x*x^n), A) ))}
    M(n, m=n)={Mat(vector(m+1, k, Col(ColGf(k-1, n), -(n+1))))}
    { my(A=M(10)); for(n=1, #A, print(A[n, 1..n])) } \\ Andrew Howroyd, Jan 18 2023

Extensions

Terms a(36) and beyond from Andrew Howroyd, Jan 18 2023

A339647 Number of inequivalent leaf colorings of series-reduced planted trees with n leaves using exactly 2 colors.

Original entry on oeis.org

0, 1, 3, 17, 73, 369, 1795, 9192, 47324, 249164, 1326449, 7155620, 38979373, 214304435, 1187338427, 6624057963, 37178881395, 209802434879, 1189621738769, 6774546637528, 38729276531965, 222191966031306, 1278819536137209, 7381798618249920, 42724974018583842
Offset: 1

Views

Author

Andrew Howroyd, Dec 16 2020

Keywords

Comments

Equivalence is up to permutation of the colors.

Examples

			a(2) = 1: (12).
a(3) = 3: (112), (1(12)), (1(22)).
a(4) = 17: (1112), (1122), (11(12)), (11(22)), (12(11)), (12(12)), (1(112)), (1(122)), (1(222)), (1(1(12))), (1(1(22))), (1(2(11))), (1(2(12))), (1(2(22))), ((11)(12)), ((11)(22)), ((12)(12)).
		

Crossrefs

The case that colors may not be interchanged is A319377.
Column 2 of A339645.

Programs

  • PARI
    \\ See A339647 for cycleIndexSeries and InequivalentColoringsSeq.
    { my(S=cycleIndexSeries(20)); InequivalentColoringsSeq(S,2) - InequivalentColoringsSeq(S,1) }

A340028 Number of unlabeled 2-connected graphs with n vertices rooted at a pair of noninterchangeable vertices.

Original entry on oeis.org

0, 1, 1, 7, 55, 655, 11147, 287791, 11787747, 804475261, 94875366649, 19825870580671, 7466490852631207, 5129453728126116131, 6487332587944013948099, 15213161506747424007012971, 66536415576917924594383104139, 545371527333985035460963541248785
Offset: 1

Views

Author

Andrew Howroyd, Jan 02 2021

Keywords

Crossrefs

Programs

  • PARI
    \\ See A004115 for graphsSeries and A339645 for combinatorial species functions.
    cycleIndexSeries(n)={my(g=graphsSeries(n), gcr=sPoint(g)/g); x*sPoint(sSolve( sLog( gcr/(x*sv(1)) ), gcr ))}
    { my(N=15); Vec(OgfSeries(cycleIndexSeries(N)), -N) }

A340029 Number of unlabeled 2-connected graphs with n vertices rooted at a pair of indistinguishable vertices.

Original entry on oeis.org

0, 1, 1, 6, 37, 388, 6004, 148759, 5974184, 404509191, 47552739892, 9923861406343, 3735194287263442, 2565376853616300801, 3244070698095148283628, 7607050619214875184974489, 33269229977451262849539412860, 272689940536978851416633440863567
Offset: 1

Views

Author

Andrew Howroyd, Jan 02 2021

Keywords

Crossrefs

Programs

  • PARI
    \\ See A004115 for graphsSeries and A339645 for combinatorial species functions.
    blockGraphs(n)={my(gc=sLog(graphsSeries(n)), gcr=sPoint(gc)); intformal(x*sSolve( sLog( gcr/(x*sv(1)) ), gcr ), sv(1)) + sSolve(subst(gc, sv(1), 0), gcr)}
    cycleIndexSeries(n)={sCartProd(blockGraphs(n), x^2 * symGroupCycleIndex(2) * symGroupSeries(n-2))}
    { my(N=15); Vec(OgfSeries(cycleIndexSeries(N)), -N) }

A339233 Number of inequivalent colorings of oriented series-parallel networks with n colored elements.

Original entry on oeis.org

1, 4, 21, 165, 1609, 19236, 266251, 4175367, 72705802, 1387084926, 28689560868, 638068960017, 15158039092293, 382527449091778, 10207466648995608, 286876818184163613, 8462814670769394769, 261266723355912507073, 8419093340955799898258, 282519424041100564770142
Offset: 1

Views

Author

Andrew Howroyd, Dec 22 2020

Keywords

Comments

Equivalence is up to permutation of the colors. Any number of colors may be used. See A339228 for additional details.

Examples

			In the following examples elements in series are juxtaposed and elements in parallel are separated by '|'.
a(1) = 1: (1).
a(2) = 4: (11), (12), (1|1), (1|2).
a(3) = 21: (111), (112), (121), (122), (123), (1(1|1)), (1(1|2)), (1(2|2)), (1(2|3)), ((1|1)1), ((1|1)2), ((1|2)1), ((1|2)3), (1|1|1), (1|1|2), (1|2|3), (1|11), (1|12), (1|21), (1|22), (1|23).
		

Crossrefs

Cf. A003430 (uncolored), A339226, A339228, A339229, A339287 (unoriented), A339645.

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    cycleIndexSeries(n)={my(Z=x*sv(1), p=Z+O(x^2)); for(n=2, n, p=sEulerT(p^2/(1+p) + Z)-1); p}
    InequivalentColoringsSeq(cycleIndexSeries(15))

A339287 Number of inequivalent colorings of unoriented series-parallel networks with n colored elements.

Original entry on oeis.org

1, 4, 15, 105, 873, 9997, 134582, 2096206, 36391653, 693779666, 14346005530, 319042302578, 7579064231400, 191264021808301, 5103735168371201, 143438421861618397, 4231407420255210941, 130633362289335958866, 4209546674788934624394, 141259712052820378949746
Offset: 1

Views

Author

Andrew Howroyd, Dec 22 2020

Keywords

Comments

Equivalence is up to permutation of the colors and reversal of all parts combined in series. Any number of colors may be used. See A339282 for additional details.

Examples

			In the following examples elements in series are juxtaposed and elements in parallel are separated by '|'.
a(1) = 1: (1).
a(2) = 4: (11), (12), (1|1), (1|2).
a(3) = 15: (111), (112), (121), (123), (1(1|1)), (1(1|2)), (1(2|2)), (1(2|3)), (1|1|1), (1|1|2), (1|2|3), (1|11), (1|12), (1|22), (1|23).
		

Crossrefs

Cf. A339225 (uncolored), A339233 (oriented), A339280, A339282, A339283, A339645.

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    B(n)={my(Z=x*sv(1), p=Z+O(x^2)); for(n=2, n, p=sEulerT(p^2/(1+p) + Z)-1); p}
    cycleIndexSeries(n)={my(Z=x*sv(1), q=sRaise(B((n+1)\2), 2), s=x^2*sv(2)+q^2/(1+q), p=Z+O(x^2), t=p); for(n=1, n\2, t=Z + q*(1 + p); p=Z + sEulerT(t+(s-sRaise(t, 2))/2) - t - 1); (p+t-Z+B(n))/2}
    InequivalentColoringsSeq(cycleIndexSeries(15))

A339646 Number of inequivalent leaf colorings of series-reduced planted trees with n leaves using at most 2 colors.

Original entry on oeis.org

1, 2, 5, 22, 85, 402, 1885, 9453, 48090, 251476, 1333517, 7177585, 39048327, 214523186, 1188037961, 6626311639, 37186187183, 209826251622, 1189699762371, 6774803376279, 38730124684829, 222194778028278, 1278828889503773, 7381829822338301, 42725078403203912
Offset: 1

Views

Author

Andrew Howroyd, Dec 16 2020

Keywords

Comments

Equivalence is up to permutation of the colors.

Examples

			a(1) = 1: 1.
a(2) = 2: (11), (12).
a(3) = 5: (111), (112), (1(11)), (1(12)), (1(22)).
		

Crossrefs

The case that colors may not be interchanged is A050381.

Programs

  • PARI
    \\ See A339645 for cycleIndexSeries and InequivalentColoringsSeq.
    InequivalentColoringsSeq(cycleIndexSeries(20),2)

Formula

a(n) = A339647(n) - A000669(n).

A361367 Number of weakly 2-connected simple digraphs with n unlabeled nodes.

Original entry on oeis.org

7, 129, 7447, 1399245, 853468061, 1774125803324, 12983268697759210, 340896057593147232397, 32512334188761655225275067, 11365639780174824680535568799361, 14668665138188644335253106665956458513, 70315069858161131939222463684374769308619684
Offset: 3

Views

Author

Manfred Scheucher, Mar 09 2023

Keywords

References

  • M. Kirchweger, M. Scheucher, and S. Szeider, SAT-Based Generation of Planar Graphs, in preparation.

Crossrefs

Directed variant of A002218.

Programs

  • PARI
    \\ See links in A339645 for combinatorial species functions.
    edges(v) = {2*sum(i=2, #v, sum(j=1, i-1, gcd(v[i], v[j]))) + sum(i=1, #v, v[i]-1)}
    graphsCycleIndex(n)={my(s=0); forpart(p=n, s+=permcount(p) * 2^edges(p) * sMonomial(p)); s/n!}
    graphsSeries(n)={sum(k=0, n, graphsCycleIndex(k)*x^k) + O(x*x^n)}
    cycleIndexSeries(n)={my(g=graphsSeries(n), gc=sLog(g), gcr=sPoint(gc)); intformal(x*sSolve( sLog( gcr/(x*sv(1)) ), gcr ), sv(1)) + sSolve(subst(gc, sv(1), 0), gcr)}
    { my(N=15); Vec(-2*x^2 + OgfSeries(cycleIndexSeries(N))) } \\ Andrew Howroyd, Mar 09 2023

Extensions

Terms a(7) and beyond from Andrew Howroyd, Mar 09 2023
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