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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A309528 The number of non-equivalent distinguishing colorings of the cycle on n vertices with at most k colors (k>=1). The cycle graph is defined for n>=3; extended to n=1,2 using the closed form. Square array read by descending antidiagonals: the rows are indexed by n, the number of vertices of the cycle and the columns are indexed by k, the number of permissible colors.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 4, 3, 0, 0, 0, 0, 10, 15, 12, 1, 0, 0, 0, 20, 45, 72, 37, 2, 0, 0, 0, 35, 105, 252, 266, 117, 6, 0, 0, 0, 56, 210, 672, 1120, 1044, 333, 14, 0, 0, 0, 84, 378, 1512, 3515, 5270, 3788, 975, 30, 0, 0, 0, 120, 630, 3024, 9121, 19350, 23475, 14056, 2712, 62, 0
Offset: 1

Views

Author

Bahman Ahmadi, Aug 06 2019

Keywords

Comments

A vertex-coloring of a graph G is called distinguishing if it is only preserved by the identity automorphism of G. This notion is considered in the subject of symmetry breaking of simple (finite or infinite) graphs. Two vertex-colorings of a graph are called equivalent if there is an automorphism of the graph which preserves the colors of the vertices. Given a graph G, we use the notation Phi_k(G) to denote the number of non-equivalent distinguishing colorings of G with at most k colors. The sequence here, displays A(n,k)=Phi_k(C_n), i.e., the number of non-equivalent distinguishing colorings of the cycle C_n on n vertices with at most k colors.

Examples

			The table begins:
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...
0, 0, 1, 4, 10, 20, 35, 56, 84, 120, ...
0, 0, 3, 15, 45, 105, 210, 378, 630, 990, ...
0, 0, 12, 72, 252, 672, 1512, 3024, 5544, 9504, ...
0, 1, 37, 266, 1120, 3515, 9121, 20692, 42456, 80565, ...
0, 2, 117, 1044, 5270, 19350, 57627, 147752, 338364, 709290, ...
0, 6, 333, 3788, 23475, 102690, 355446, 1039248, 2673810, 6222150, ...
0, 14, 975, 14056, 106950, 555990, 2233469, 7440160, 21493836, 55505550, ...
0, 30, 2712, 51132, 483504, 3009426, 14089488, 53611992, 174189024, 499720518, ...
------
For n=4, we can color the vertices of the cycle C_4 with at most 3 colors, in 3 ways, such that all the colorings distinguish the graph (i.e., no non-identity automorphism of C_4 preserves the coloring) and that all the three colorings are non-equivalent. The color classes are as follows:
{ { 1 }, { 2 }, { 3, 4 } }
{ { 1 }, { 2, 3 }, { 4 } }
{ { 1, 2 }, { 3 }, { 4 } }
		

Crossrefs

Columns k=2..5 for n >= 3 are A032239, A032240, A032241, A032242.
Different from A293496.

Programs

  • PARI
    A(n,k)={sumdiv(n, d, moebius(n/d)*(k^d/n - if(d%2, k^((d+1)/2), (k+1)*k^(d/2)/2)))/2} \\ Andrew Howroyd, Aug 11 2019

Formula

A(n,k) = (A074650(n,k) - A284856(n,k))/2. - Andrew Howroyd, Aug 11 2019

A001693 Number of degree-n irreducible polynomials over GF(7); dimensions of free Lie algebras.

Original entry on oeis.org

1, 7, 21, 112, 588, 3360, 19544, 117648, 720300, 4483696, 28245840, 179756976, 1153430600, 7453000800, 48444446376, 316504099520, 2077057800300, 13684147881600, 90467419857752, 599941851861744
Offset: 0

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Author

Keywords

Comments

Number of aperiodic necklaces with n beads of 7 colors. - Herbert Kociemba, Nov 25 2016

References

  • E. R. Berlekamp, Algebraic Coding Theory, McGraw-Hill, NY, 1968, p. 84.
  • M. Lothaire, Combinatorics on Words. Addison-Wesley, Reading, MA, 1983, p. 79.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column 7 of A074650.

Programs

  • Maple
    with(numtheory); A001693 := proc(n) local d,s; if n = 0 then RETURN(1); else s := 0; for d in divisors(n) do s := s+mobius(d)*7^(n/d); od; RETURN(s/n); fi; end;
  • Mathematica
    a[n_]:=(1/n)*Sum[MoebiusMu[d]*7^(n/d), {d, Divisors[n]}]; a[0] = 1; Table[a[n], {n, 0, 19}] (* Jean-François Alcover, Aug 31 2011, after formula *)
    mx=40;f[x_,k_]:=1-Sum[MoebiusMu[i] Log[1-k*x^i]/i,{i,1,mx}];CoefficientList[Series[f[x,7],{x,0,mx}],x] (* Herbert Kociemba, Nov 25 2016 *)
  • PARI
    a(n) = if(n, sumdiv(n, d, moebius(d)*7^(n/d))/n, 1) \\ Altug Alkan, Dec 01 2015

Formula

a(n) = (1/n)*Sum_{d|n} mu(d)*7^(n/d), for n>0.
G.f.: k=7, 1 - Sum_{i>=1} mu(i)*log(1 - k*x^i)/i. - Herbert Kociemba, Nov 25 2016

Extensions

Description corrected by Vladeta Jovovic, Feb 09 2001

A027380 Number of irreducible polynomials of degree n over GF(8); dimensions of free Lie algebras.

Original entry on oeis.org

1, 8, 28, 168, 1008, 6552, 43596, 299592, 2096640, 14913024, 107370900, 780903144, 5726600880, 42288908760, 314146029564, 2345624803704, 17592184995840, 132458812569720, 1000799909722368, 7585009898729256
Offset: 0

Views

Author

Keywords

Comments

Number of Lyndon words with 8 letters. - Joerg Arndt, Jul 29 2014
Number of aperiodic necklaces with n beads of 8 colors. - Herbert Kociemba, Nov 25 2016

Examples

			G.f. = 1 + 8*x + 28*x^2 + 168*x^3 + 1008*x^4 + 6552*x^5 + 43596*x^6 + ...
		

References

  • E. R. Berlekamp, Algebraic Coding Theory, McGraw-Hill, NY, 1968, p. 84.
  • M. Lothaire, Combinatorics on Words. Addison-Wesley, Reading, MA, 1983, p. 79.

Crossrefs

Column 8 of A074650.

Programs

  • Maple
    A027380 := proc(n)
        local d;
        if n = 0 then
            1;
        else
            add( 8^(n/d)*numtheory[mobius](d),d=numtheory[divisors](n)) ;
            %/n ;
        end if;
    end proc: # R. J. Mathar, Jun 09 2016
  • Mathematica
    f[n_] := (1/n)*Sum[MoebiusMu[d]*8^(n/d), {d, Divisors[n]}]; f[0] = 1; Array[f, 20, 0] (* Robert G. Wilson v, Jul 28 2014 *)
    mx=40;f[x_,k_]:=1-Sum[MoebiusMu[i] Log[1-k*x^i]/i,{i,1,mx}];CoefficientList[Series[f[x,8],{x,0,mx}],x] (* Herbert Kociemba, Nov 25 2016 *)
  • PARI
    a(n) = if(n, sumdiv(n, d, moebius(d)*8^(n/d))/n, 1) \\ Altug Alkan, Dec 01 2015

Formula

G.f.: k=8, 1 - Sum_{i>=1} mu(i)*log(1 - k*x^i)/i. - Herbert Kociemba, Nov 25 2016
a(n) = Sum_{d|n} mu(d)*8^(n/d)/n for n > 0. - Andrew Howroyd, Oct 13 2017

A027381 Number of irreducible polynomials of degree n over GF(9); dimensions of free Lie algebras.

Original entry on oeis.org

1, 9, 36, 240, 1620, 11808, 88440, 683280, 5380020, 43046640, 348672528, 2852823600, 23535749880, 195528140640, 1634056262280, 13726075468992, 115813759112820, 981010688215680, 8338590828280440, 71097458824894320
Offset: 0

Views

Author

Keywords

Comments

Number of aperiodic necklaces with n beads of 9 colors. - Herbert Kociemba, Nov 25 2016

Examples

			G.f. = 1 + 9*x + 36*x^2 + 240*x^3 + 1620*x^4 + 11808*x^5 + 88440*x^6 + ...
		

References

  • E. R. Berlekamp, Algebraic Coding Theory, McGraw-Hill, NY, 1968, p. 84.
  • M. Lothaire, Combinatorics on Words. Addison-Wesley, Reading, MA, 1983, p. 79.

Crossrefs

Column 9 of A074650.
Cf. A001037.

Programs

  • Mathematica
    f[n_] := (1/n)*Sum[ MoebiusMu[d]*9^(n/d), {d, Divisors[n]}]; f[0] = 1; Array[f, 20, 0] (* Robert G. Wilson v, Jul 28 2014 *)
    mx=40;f[x_,k_]:=1-Sum[MoebiusMu[i] Log[1-k*x^i]/i,{i,1,mx}];CoefficientList[Series[f[x,9],{x,0,mx}],x] (* Herbert Kociemba, Nov 25 2016 *)
  • PARI
    a(n) = if(n, sumdiv(n, d, moebius(d)*9^(n/d))/n, 1) \\ Altug Alkan, Dec 01 2015

Formula

G.f.: k=9, 1 - Sum_{i>=1} mu(i)*log(1 - k*x^i)/i. - Herbert Kociemba, Nov 25 2016
a(n) = Sum_{d|n} mu(d)*9^(n/d)/n for n > 0. - Andrew Howroyd, Oct 13 2017

A252764 Number of length n primitive (=aperiodic or period n) n-ary words.

Original entry on oeis.org

1, 2, 24, 240, 3120, 46410, 823536, 16773120, 387419760, 9999899910, 285311670600, 8916097441680, 302875106592240, 11112006720144330, 437893890380096640, 18446744069414584320, 827240261886336764160, 39346408075098144278664, 1978419655660313589123960
Offset: 1

Views

Author

Alois P. Heinz, Dec 21 2014

Keywords

Examples

			a(3) = 24 because there are 24 primitive words of length 3 over 3-letter alphabet {a,b,c}: aab, aac, aba, abb, abc, aca, acb, acc, baa, bab, bac, bba, bbc, bca, bcb, bcc, caa, cab, cac, cba, cbb, cbc, cca, ccb.
		

Crossrefs

Main diagonal of A143324.

Programs

  • Maple
    with(numtheory):
    a:= n-> add(n^d *mobius(n/d), d=divisors(n)):
    seq(a(n), n=1..25);
  • Mathematica
    a[n_] := DivisorSum[n, n^# * MoebiusMu[n/#]& ];
    Array[a, 25] (* Jean-François Alcover, Mar 24 2017, translated from Maple *)

Formula

a(n) = Sum_{d|n} n^d * mu(n/d), mu = A008683.
a(n) = A075147(n)*n.
a(n) = A074650(n,n) * n.
a(n) = A143325(n,n) * n.
a(n) = A143324(n,n).

A320071 Number of length n primitive (=aperiodic or period n) 6-ary words which are earlier in lexicographic order than any other word derived by cyclic shifts of the alphabet.

Original entry on oeis.org

1, 5, 35, 210, 1295, 7735, 46655, 279720, 1679580, 10076395, 60466175, 362789070, 2176782335, 13060647355, 78364162765, 470184704640, 2821109907455, 16926657757380, 101559956668415, 609359729932590, 3656158440016285, 21936950579911675, 131621703842267135
Offset: 1

Views

Author

Alois P. Heinz, Oct 05 2018

Keywords

Comments

Dirichlet convolution of mu(n) with 6^(n-1).

Crossrefs

Column k=6 of A143325.
First differences of A320090.

Programs

  • Maple
    a:= n-> add(`if`(d=n, 6^(n-1), -a(d)), d=numtheory[divisors](n)):
    seq(a(n), n=1..25);
  • Mathematica
    nmax = 20; Rest[CoefficientList[Series[Sum[MoebiusMu[k] * x^k / (1 - 6*x^k), {k, 1, nmax}], {x, 0, nmax}], x]] (* Vaclav Kotesovec, Dec 11 2020 *)

Formula

a(n) = Sum_{d|n} 6^(d-1) * mu(n/d).
a(n) = 6^(n-1) - Sum_{d
a(n) = A143325(n,6).
a(n) = A074650(n,6) * n/6.
a(n) = A143324(n,6) / 6.
G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 6*x^k). - Ilya Gutkovskiy, Oct 25 2018

A320072 Number of length n primitive (=aperiodic or period n) 7-ary words which are earlier in lexicographic order than any other word derived by cyclic shifts of the alphabet.

Original entry on oeis.org

1, 6, 48, 336, 2400, 16752, 117648, 823200, 5764752, 40351200, 282475248, 1977309600, 13841287200, 96888892752, 678223070400, 4747560686400, 33232930569600, 232630508205648, 1628413597910448, 11398895145019200, 79792266297494304, 558545863800808752
Offset: 1

Author

Alois P. Heinz, Oct 05 2018

Keywords

Comments

Dirichlet convolution of mu(n) with 7^(n-1).

Crossrefs

Column k=7 of A143325.
First differences of A320091.

Programs

  • Maple
    a:= n-> add(`if`(d=n, 7^(n-1), -a(d)), d=numtheory[divisors](n)):
    seq(a(n), n=1..25);

Formula

a(n) = Sum_{d|n} 7^(d-1) * mu(n/d).
a(n) = 7^(n-1) - Sum_{d
a(n) = A143325(n,7).
a(n) = A074650(n,7) * n/7.
a(n) = A143324(n,7) / 7.
G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 7*x^k). - Ilya Gutkovskiy, Oct 25 2018

A320073 Number of length n primitive (=aperiodic or period n) 8-ary words which are earlier in lexicographic order than any other word derived by cyclic shifts of the alphabet.

Original entry on oeis.org

1, 7, 63, 504, 4095, 32697, 262143, 2096640, 16777152, 134213625, 1073741823, 8589901320, 68719476735, 549755551737, 4398046506945, 35184369991680, 281474976710655, 2251799796875328, 18014398509481983, 144115187941637640, 1152921504606584769
Offset: 1

Author

Alois P. Heinz, Oct 05 2018

Keywords

Comments

Dirichlet convolution of mu(n) with 8^(n-1).

Crossrefs

Column k=8 of A143325.
First differences of A320092.

Programs

  • Maple
    a:= n-> add(`if`(d=n, 8^(n-1), -a(d)), d=numtheory[divisors](n)):
    seq(a(n), n=1..25);

Formula

a(n) = Sum_{d|n} 8^(d-1) * mu(n/d).
a(n) = 8^(n-1) - Sum_{d
a(n) = A143325(n,8).
a(n) = A074650(n,8) * n/8.
a(n) = A143324(n,8) / 8.
G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 8*x^k). - Ilya Gutkovskiy, Oct 25 2018

A320074 Number of length n primitive (=aperiodic or period n) 9-ary words which are earlier in lexicographic order than any other word derived by cyclic shifts of the alphabet.

Original entry on oeis.org

1, 8, 80, 720, 6560, 58960, 531440, 4782240, 43046640, 387413920, 3486784400, 31380999840, 282429536480, 2541865296880, 22876792448320, 205891127311680, 1853020188851840, 16677181656560880, 150094635296999120, 1350851717285570880, 12157665459056397280
Offset: 1

Author

Alois P. Heinz, Oct 05 2018

Keywords

Comments

Dirichlet convolution of mu(n) with 9^(n-1).

Crossrefs

Column k=9 of A143325.
First differences of A320093.

Programs

  • Maple
    a:= n-> add(`if`(d=n, 9^(n-1), -a(d)), d=numtheory[divisors](n)):
    seq(a(n), n=1..25);

Formula

a(n) = Sum_{d|n} 9^(d-1) * mu(n/d).
a(n) = 9^(n-1) - Sum_{d
a(n) = A143325(n,9).
a(n) = A074650(n,9) * n/9.
a(n) = A143324(n,9) / 9.
G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 9*x^k). - Ilya Gutkovskiy, Oct 25 2018

A006177 Witt vector *2!/2!.

Original entry on oeis.org

1, 1, 3, 8, 25, 72, 245, 772, 2692, 8925, 32065, 109890, 400023, 1402723, 5165327, 18484746, 68635477, 248339122, 930138521, 3406231198, 12810761323, 47306348881, 178987624513, 665627041157, 2528210175630, 9456885664122
Offset: 1

Author

Keywords

Comments

The Somos transform sends sequence {a(n)} to sequence with g.f. Product_{i=1..n} 1/(1-a(i)*x^i).
If c is the Witt transform of b then b(n) = Sum_{d|n} A074650(n/d, c(d)).

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Formula

Inverse Somos transform of A000108. - Wouter Meeussen, Aug 20 2002
Witt transform of A022553.

Extensions

Edited by Christian G. Bower, Aug 20 2002, Aug 28 2002
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