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.

Showing 1-6 of 6 results.

A074761 Number of partitions of n of order n.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 9, 1, 4, 5, 1, 1, 12, 1, 27, 7, 6, 1, 81, 1, 7, 1, 54, 1, 407, 1, 1, 11, 9, 13, 494, 1, 10, 13, 423, 1, 981, 1, 137, 115, 12, 1, 1309, 1, 59, 17, 193, 1, 240, 21, 1207, 19, 15, 1, 47274, 1, 16, 239, 1, 25, 3284, 1, 333, 23, 3731, 1, 42109, 1, 19
Offset: 1

Views

Author

Vladeta Jovovic, Sep 28 2002

Keywords

Comments

Order of partition is lcm of its parts.
a(n) is the number of conjugacy classes of the symmetric group S_n such that a representative of the class has order n. Here order means the order of an element of a group. Note that a(n) = 1 if and only if n is a prime power. - W. Edwin Clark, Aug 05 2014

Examples

			The a(15) = 5 partitions are (15), (5,3,3,3,1), (5,5,3,1,1), (5,3,3,1,1,1,1), (5,3,1,1,1,1,1,1,1). - _Gus Wiseman_, Aug 01 2018
		

Crossrefs

Programs

  • Maple
    A:= proc(n)
          uses numtheory;
          local S;
        S:= add(mobius(n/i)*1/mul(1-x^j,j=divisors(i)),i=divisors(n));
        coeff(series(S,x,n+1),x,n);
    end proc:
    seq(A(n),n=1..100); # Robert Israel, Aug 06 2014
  • Mathematica
    a[n_] := With[{s = Sum[MoebiusMu[n/i]*1/Product[1-x^j, {j, Divisors[i]}], {i, Divisors[n]}]}, SeriesCoefficient[s, {x, 0, n}]]; Array[a, 80] (* Jean-François Alcover, Feb 29 2016 *)
    Table[Length[Select[IntegerPartitions[n],LCM@@#==n&]],{n,50}] (* Gus Wiseman, Aug 01 2018 *)
  • PARI
    pr(k, x)={my(t=1); fordiv(k, d, t *= (1-x^d) ); return(t); }
    a(n) =
    {
        my( x = 'x+O('x^(n+1)) );
        polcoeff( Pol( sumdiv(n, i, moebius(n/i) / pr(i, x) ) ), n );
    }
    vector(66, n, a(n) )
    \\ Joerg Arndt, Aug 06 2014

Formula

Coefficient of x^n in expansion of Sum_{i divides n} A008683(n/i)*1/Product_{j divides i} (1-x^j).

A057731 Irregular triangle read by rows: T(n,k) = number of elements of order k in symmetric group S_n, for n >= 1, 1 <= k <= g(n), where g(n) = A000793(n) is Landau's function.

Original entry on oeis.org

1, 1, 1, 1, 3, 2, 1, 9, 8, 6, 1, 25, 20, 30, 24, 20, 1, 75, 80, 180, 144, 240, 1, 231, 350, 840, 504, 1470, 720, 0, 0, 504, 0, 420, 1, 763, 1232, 5460, 1344, 10640, 5760, 5040, 0, 4032, 0, 3360, 0, 0, 2688, 1, 2619, 5768, 30996, 3024, 83160, 25920, 45360, 40320, 27216, 0, 30240, 0, 25920, 24192, 0, 0, 0, 0, 18144
Offset: 1

Views

Author

Roger Cuculière, Oct 29 2000

Keywords

Comments

Every row for n >= 7 contains zeros. Landau's function quickly becomes > 2*n, and there is always a prime between n and 2*n. T(n,p) = 0 for such a prime p. - Franklin T. Adams-Watters, Oct 25 2011

Examples

			Triangle begins:
  1;
  1,   1;
  1,   3,   2;
  1,   9,   8,   6;
  1,  25,  20,  30,  24,   20;
  1,  75,  80, 180, 144,  240;
  1, 231, 350, 840, 504, 1470, 720, 0, 0, 504, 0, 420;
  ...
		

References

  • Herbert S. Wilf, "The asymptotics of e^P(z) and the number of elements of each order in S_n." Bull. Amer. Math. Soc., 15.2 (1986), 225-232.

Crossrefs

Cf. A000793, also A054522 (for cyclic group), A057740 (alternating group), A057741 (dihedral group).
Rows sums give A000142, last elements of rows give A074859, columns k=2, 3, 5, 7, 11 give A001189, A001471, A059593, A153760, A153761. - Alois P. Heinz, Feb 16 2013
Main diagonal gives A074351.
Cf. A222029.

Programs

  • Magma
    {* Order(g) : g in Sym(6) *};
    
  • Maple
    with(group):
    for n from 1 do
        f := [seq(0,i=1..n!)] ;
        mknown := 0 ;
        # loop through the permutations of n
        Sn := combinat[permute](n) ;
        for per in Sn do
            # write this permutation in cycle notation
            gen := convert(per,disjcyc) ;
            # compute the list of lengths of the cycles, then the lcm of these
            cty := [seq(nops(op(i,gen)),i=1..nops(gen))] ;
            if cty <> [] then
                lcty := lcm(op(cty)) ;
            else
                lcty := 1 ;
            end if;
            f := subsop(lcty = op(lcty,f)+1,f) ;
            mknown := max(mknown,lcty) ;
        end do:
        ff := add(el,el=f) ;
        print(seq(f[i],i=1..mknown)) ;
    end do: # R. J. Mathar, May 26 2014
    # second Maple program:
    b:= proc(n, g) option remember; `if`(n=0, x^g, add((j-1)!
          *b(n-j, ilcm(g, j))*binomial(n-1, j-1), j=1..n))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=1..degree(p)))(b(n, 1)):
    seq(T(n), n=1..12);  # Alois P. Heinz, Jul 11 2017
  • Mathematica
    <Jean-François Alcover, Aug 31 2016 *)
    b[n_, g_] := b[n, g] = If[n == 0, x^g, Sum[(j-1)!*b[n-j, LCM[g, j]]* Binomial[n-1, j-1], {j, 1, n}]];
    T[n_] := Function[p, Table[Coefficient[p, x, i], {i, 1, Exponent[p, x]}]][ b[n, 1]];
    Array[T, 12] // Flatten (* Jean-François Alcover, May 03 2019, after Alois P. Heinz *)
  • PARI
    T(n,k)={n!*polcoeff(sumdiv(k, i, moebius(k/i)*exp(sumdiv(i, j, x^j/j) + O(x*x^n))), n)} \\ Andrew Howroyd, Jul 02 2018

Formula

Sum_{k=1..A000793(n)} k*T(n,k) = A060014(n); A000793 = Landau's function.

Extensions

More terms from N. J. A. Sloane, Nov 01 2000

A074759 Number of degree-n permutations of order dividing n. Number of solutions to x^n = 1 in S_n.

Original entry on oeis.org

1, 1, 2, 3, 16, 25, 396, 721, 11264, 46089, 602200, 3628801, 133494912, 479001601, 7692266960, 95904273375, 1914926104576, 20922789888001, 628693317946656, 6402373705728001, 182635841123840000, 2496321046987530021, 55826951075231672512, 1124000727777607680001
Offset: 0

Views

Author

Vladeta Jovovic, Sep 28 2002

Keywords

Crossrefs

Main diagonal of A008307.

Programs

  • Maple
    A:= proc(n,k) option remember; `if`(n<0, 0, `if`(n=0, 1,
           add(mul(n-i, i=1..j-1)*A(n-j,k), j=numtheory[divisors](k))))
        end:
    a:= n-> A(n, n):
    seq(a(n), n=0..25);  # Alois P. Heinz, Feb 14 2013
  • Mathematica
    Table[a = Sum[x^i/i, {i, Divisors[n]}]; Part[Range[0, 20]! CoefficientList[Series[Exp[a], {x, 0, 20}], x],n + 1], {n, 0, 20}]  (* Geoffrey Critzer, Dec 04 2011 *)

Formula

a(n) = n! * [x^n] exp(Sum_{k divides n} x^k/k).
a(n) = Sum_{d|n} A057731(n,d) for n >= 1. - Alois P. Heinz, Jul 05 2021

A290961 Number of endofunctions on [n] such that the LCM of their cycle lengths equals n.

Original entry on oeis.org

1, 1, 2, 6, 24, 840, 720, 5040, 40320, 59814720, 3628800, 83701537920, 479001600, 26980643289600, 2642646473026560, 1307674368000, 20922789888000, 41837259585747225600, 6402373705728000, 598354114828973074790400, 18160977780223038067507200
Offset: 1

Views

Author

Alois P. Heinz, Aug 15 2017

Keywords

Crossrefs

Main diagonal of A222029.
Cf. A074351 (the same for permutations).

Programs

  • Maple
    b:= proc(n, m) option remember; `if`(n=0, x^m, add((j-1)!*
          b(n-j, ilcm(m, j))*binomial(n-1, j-1), j=1..n))
        end:
    a:= n-> add(coeff(b(j, 1), x, n)*n^(n-j)*binomial(n-1, j-1), j=0..n):
    seq(a(n), n=1..25);
  • Mathematica
    b[n_, m_] := b[n, m] = If[n == 0, x^m, Sum[(j - 1)!*
         b[n - j, LCM[m, j]]*Binomial[n - 1, j - 1], {j, 1, n}]];
    a[n_] := Sum[Coefficient[b[j, 1], x, n]*n^(n-j)*Binomial[n-1, j-1], {j, 0, n}];
    Table[a[n], {n, 1, 25}] (* Jean-François Alcover, Mar 07 2022, after Alois P. Heinz *)

Formula

a(n) = A222029(n,n).

A074880 Number of labeled cyclic subgroups of S_n having order n.

Original entry on oeis.org

1, 1, 1, 3, 6, 120, 120, 1260, 6720, 128520, 362880, 20041560, 39916800, 1132971840, 11721790080, 163459296000, 1307674368000, 87307501881600, 355687428096000, 19137704006453760, 205947392645030400, 5118231678995635200, 51090942171709440000, 4769913628444053196800
Offset: 1

Views

Author

Vladeta Jovovic, Sep 30 2002

Keywords

Crossrefs

Programs

  • PARI
    a(n)={n!*polcoeff(sumdiv(n, i, moebius(n/i)*exp(sumdiv(i, j, x^j/j) + O(x*x^n))), n)/eulerphi(n)} \\ Andrew Howroyd, Jul 02 2018

Formula

a(n) = A074351(n)/A000010(n).

Extensions

Terms a(22) and beyond from Andrew Howroyd, Jul 02 2018

A346121 Number of permutations of [n] whose order is a multiple of n.

Original entry on oeis.org

1, 1, 2, 6, 24, 240, 720, 5040, 40320, 816480, 3628800, 108108000, 479001600, 14789174400, 254431457280, 1307674368000, 20922789888000, 872545722048000, 6402373705728000, 411616608508385280, 7817896752906240000, 128126503414990080000, 1124000727777607680000
Offset: 1

Views

Author

Alois P. Heinz, Jul 05 2021

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, g) option remember; `if`(n=0, x^g, add((j-1)!
          *b(n-j, ilcm(g, j))*binomial(n-1, j-1), j=1..n))
        end:
    a:= n-> (p-> add(coeff(p, x, i*n), i=1..degree(p)/n))(b(n, 1)):
    seq(a(n), n=1..23);
    # second Maple program:
    h:= proc(n, j) option remember; uses padic, numtheory; n/mul(`if`(
          ordp(j, p) b(n$2):
    seq(a(n), n=1..23);
  • Mathematica
    b[n_, g_] := b[n, g] = If[n == 0, x^g, Sum[(j - 1)!*b[n - j, LCM[g, j]]* Binomial[n - 1, j - 1], {j, 1, n}]] // Expand;
    a[n_] := With[{p = b[n, 1]}, Sum[Coefficient[p, x, i*n], {i, 1, Exponent[p, x]/n}]];
    Array[a, 40] (* Jean-François Alcover, Aug 23 2021, after Alois P. Heinz's first program *)

Formula

a(n) = Sum_{i>=1} A057731(n,i*n).
a(n) = (n-1)! <=> n in { A000961 }.
a(n) = A057731(n,n) = A074351(n) = A052699(n-1) for n <= 9.
Showing 1-6 of 6 results.