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 1-10 of 80 results. Next

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

A074859 Number of elements of S_n having the maximum possible order g(n), where g(n) is Landau's function (A000793).

Original entry on oeis.org

1, 1, 1, 2, 6, 20, 240, 420, 2688, 18144, 120960, 2661120, 7983360, 103783680, 1037836800, 12454041600, 149448499200, 1693749657600, 60974987673600, 289631191449600, 5792623828992000, 121645100408832000, 3568256278659072000, 30776210403434496000, 738629049682427904000, 12310484161373798400000
Offset: 0

Views

Author

Christopher J. Smyth, Sep 11 2002

Keywords

References

  • J.-L. Nicolas, On Landau's function g(n), pp. 228-240 of R. L. Graham et al., eds., Mathematics of Paul Erdős I.

Crossrefs

Cf. A000793 (Landau's function g(n)).
Last row element of A057731. - Alois P. Heinz, Feb 14 2013

Programs

  • Mathematica
    g[n_] := Max[ Apply[ LCM, IntegerPartitions[n], 1]]; f[x_, n_] := Total[ (MoebiusMu[g[n]/#]*Exp[ Total[ (x^#/# & ) /@ Divisors[#]]] & ) /@ Divisors[g[n]]]; a[n_] := n!*Coefficient[ Series[f[x, n], {x, 0, n}], x^n]; Table[a[n], {n, 1, 25}] (* Jean-François Alcover, Nov 03 2011, after Vladeta Jovovic *)

Formula

a(n) = n!*coefficient of x^n in expansion of Sum_{i divides A000793(n)} mu(A000793(n)/i)*exp(Sum_{j divides i} x^j/j). - Vladeta Jovovic, Sep 29 2002

Extensions

Corrected and extended by Vladeta Jovovic, Sep 20 2002

A002809 Increasing values of A000793 (largest order of permutation of n elements).

Original entry on oeis.org

1, 2, 3, 4, 6, 12, 15, 20, 30, 60, 84, 105, 140, 210, 420, 840, 1260, 1540, 2310, 2520, 4620, 5460, 9240, 13860, 16380, 27720, 30030, 32760, 60060, 120120, 180180, 360360, 471240, 510510, 556920, 1021020, 1141140, 2042040, 3063060, 3423420, 6126120, 6846840
Offset: 1

Views

Author

Keywords

References

  • 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

Indices are A006644.
Cf. A000793.

Programs

  • Mathematica
    b[n_, i_] := b[n, i] = Module[{p}, p = If[i<1, 1, Prime[i]]; If[n == 0 || i<1, 1, Max[b[n, i-1], Table[p^j*b[n-p^j, i-1], {j, 1, Log[p, n] // Floor}]]]]; a[n_] := b[n, If[n<8, 3, PrimePi[Ceiling[1.328*Sqrt[n*Log[n] // Floor]]]]]; Table[a[n], {n, 0, 100}] // Union (* Jean-François Alcover, Mar 07 2014, after Alois P. Heinz *)

Extensions

Description improved Apr 15 1997. More terms from David W. Wilson.

A225558 a(n) = A003418(n)/A000793(n).

Original entry on oeis.org

1, 1, 1, 2, 3, 10, 10, 35, 56, 126, 84, 924, 462, 6006, 4290, 3432, 5148, 58344, 58344, 554268, 554268, 554268, 554268, 6374082, 6374082, 21246940, 21246940, 52151580, 34767720, 924241890, 504131940, 15628090140, 26447537160, 26447537160, 15628090140
Offset: 0

Views

Author

Antti Karttunen, May 10 2013

Keywords

Crossrefs

Programs

  • Maple
    g:= proc(n) g(n):= `if`(n=0, 1, ilcm(n, g(n-1))) end:
    b:= proc(n, i) option remember; local p;
          p:= `if`(i<1, 1, ithprime(i));
          `if`(n=0 or i<1, 1, max(b(n, i-1),
               seq(p^j*b(n-p^j, i-1), j=1..ilog[p](n))))
        end:
    a:= n->g(n)/b(n, `if`(n<8, 3,
        numtheory[pi](ceil(1.328*isqrt(n*ilog(n)))))):
    seq(a(n), n=0..40); # Alois P. Heinz, May 22 2013
  • Mathematica
    b[n_, i_] := b[n, i] = Module[{p}, p = If[i<1, 1, Prime[i]]; If[n==0 || i<1, 1, Max[b[n, i-1], Table[p^j*b[n-p^j, i-1], {j, 1, Log[p, n] // Floor }]]]]; a[0]=1; a[n_] := LCM @@ Range[n] / b[n, If[n<8, 3, PrimePi[ Ceiling[ 1.328*Sqrt[n*Log[n] // Floor]]]]]; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Feb 27 2016, after Alois P. Heinz *)

Formula

a(n) = A003418(n)/A000793(n).
A074115(n)/a(n) = A025527(n).

A225636 a(n) = A225627(n)/A000793(n).

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 5, 7, 8, 9, 7, 14, 11, 13, 15, 44, 39, 26, 26, 22, 33, 33, 39, 39, 143, 143, 143, 153, 78, 187, 221, 221, 209, 209, 247, 247, 323, 323, 418, 418, 391, 646, 437, 437, 646, 969, 969, 969, 969, 782, 874, 874, 1292, 667, 713, 713, 782, 5681, 3496
Offset: 0

Views

Author

Antti Karttunen, May 13 2013

Keywords

Comments

a(n) divides A225558(n) for all n.

Crossrefs

Programs

A225648 Positions of ones in A225650, numbers n such that n and A000793(n) are coprime.

Original entry on oeis.org

0, 1, 5, 7, 8, 9, 11, 13, 17, 19, 23, 27, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313
Offset: 1

Views

Author

Antti Karttunen, May 12 2013

Keywords

Comments

Contains all primes from 5 onward. Are 8, 9 and 27 only composite numbers present?

Crossrefs

Complement: A225649. Cf. also A225650.

Programs

  • Mathematica
    b[n_, i_] := b[n, i] = Module[{p}, p = If[i < 1, 1, Prime[i]]; If[n == 0 || i < 1, 1, Max[b[n, i - 1], Table[p^j*b[n - p^j, i - 1], {j, 1, Log[p, n] // Floor}]]]]; g[n_] := b[n, If[n < 8, 3, PrimePi[Ceiling[1.328*Sqrt[n* Log[n] // Floor]]]]]; Join[{0}, Position[Table[GCD[n, g[n]], {n, 1, 500} ], 1] // Flatten] (* Jean-François Alcover, Mar 03 2016, after Alois P. Heinz *)

A225651 Numbers k that divide A000793(k).

Original entry on oeis.org

1, 2, 3, 4, 6, 10, 12, 14, 15, 20, 21, 24, 30, 35, 36, 39, 40, 42, 44, 52, 55, 56, 60, 65, 66, 70, 72, 76, 77, 78, 84, 85, 90, 91, 95, 99, 102, 105, 110, 114, 115, 117, 119, 120, 126, 130, 132, 133, 136, 138, 140, 143, 152, 153, 154, 155, 156, 161, 165, 170
Offset: 1

Views

Author

Antti Karttunen, May 16 2013

Keywords

Comments

After 1, a subset of A225649.
Also, for all n, A225650(a(n)) = a(n) and A225655(a(n)) = A000793(a(n)).

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; local p;
          p:= `if`(i<1, 1, ithprime(i));
          `if`(n=0 or i<1, 1, max(b(n, i-1),
               seq(p^j*b(n-p^j, i-1), j=1..ilog[p](n))))
        end:
    g:=n->b(n, `if`(n<8, 3, numtheory[pi](ceil(1.328*isqrt(n*ilog(n)))))):
    a:= proc(n) option remember; local k;
          for k from 1+`if`(n=1, 0, a(n-1))
          while not irem(g(k), k)=0 do od; k
        end:
    seq(a(n), n=1..70);  # Alois P. Heinz, May 22 2013
  • Mathematica
    Reap[For[n=1, n <= 40, n++, If[Divisible[Max[LCM @@@ IntegerPartitions[n] ], n], Sow[n]]]][[2, 1]]
    (* or, for a large number of terms: *)
    b[n_, i_] := b[n, i] = Module[{p}, p = If[i<1, 1, Prime[i]]; If[n==0 || i<1, 1, Max[b[n, i-1], Table[p^j*b[n - p^j, i-1], {j, 1, Log[p, n] // Floor}]]]]; g[n_] := b[n, If[n<8, 3, PrimePi[Ceiling[1.328*Sqrt[n*Log[n] // Floor]]]]]; Reap[For[k=1, k <= 1000, k++, If[Divisible[g[k], k], Sow[ k]]]][[2, 1]] (* Jean-François Alcover, Feb 28 2016, after Alois P. Heinz *)

A225649 Positions of non-ones in A225650, numbers n such that n and A000793(n) have at least one common divisor > 1.

Original entry on oeis.org

2, 3, 4, 6, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92
Offset: 1

Views

Author

Antti Karttunen, May 13 2013

Keywords

Comments

Which composites are missing apart from 8, 9 and 27? See comment at A225648.

Crossrefs

Cf. A225648 (complement), A225651 (from n>1 onward is a subset).

A074115 a(n) = n!/A000793(n).

Original entry on oeis.org

1, 1, 1, 2, 6, 20, 120, 420, 2688, 18144, 120960, 1330560, 7983360, 103783680, 1037836800, 12454041600, 149448499200, 1693749657600, 30487493836800, 289631191449600, 5792623828992000, 121645100408832000, 2676192208994304000, 30776210403434496000
Offset: 0

Views

Author

Vladeta Jovovic, Sep 16 2002

Keywords

Crossrefs

Cf. A074859.

Extensions

a(0)=1 prepended by Alois P. Heinz, Jul 12 2017

A074881 Triangle T(n,k) giving number of labeled cyclic subgroups of order k in symmetric group S_n, 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, 1, 1, 9, 4, 3, 1, 25, 10, 15, 6, 10, 1, 75, 40, 90, 36, 120, 1, 231, 175, 420, 126, 735, 120, 126, 105, 1, 763, 616, 2730, 336, 5320, 960, 1260, 1008, 840, 336, 1, 2619, 2884, 15498, 756, 41580, 4320, 11340, 6720, 6804, 7560, 4320, 3024, 2268
Offset: 1

Views

Author

Vladeta Jovovic, Sep 30 2002

Keywords

Comments

A057731 contains zeros. This sequence contains only positive values of A057731(n,k)/A000010(k). - Alois P. Heinz, Feb 16 2013

Examples

			Triangle begins:
  1;
  1,   1;
  1,   3,   1;
  1,   9,   4,   3;
  1,  25,  10,  15,   6,  10;
  1,  75,  40,  90,  36, 120;
  1, 231, 175, 420, 126, 735, 120, 126, 105;
  ...
		

Crossrefs

Row sums give A051625.

Programs

  • Mathematica
    nmax = 10;
    T[n_, k_] := n! SeriesCoefficient[O[x]^(n+1) + Sum[MoebiusMu[k/i]*Exp[ Sum[x^j/j, {j, Divisors[i]}]], {i, Divisors[k]}], {x, 0, n}]/ EulerPhi[k];
    Table[DeleteCases[Table[T[n, k], {k, 1, 2 nmax}], 0], {n, 1, nmax}] // Flatten (* Jean-François Alcover, Sep 16 2019, after Andrew Howroyd *)
  • PARI
    T(n,k)={n!*polcoeff(sumdiv(k, i, moebius(k/i)*exp(sumdiv(i, j, x^j/j) + O(x*x^n))), n)/eulerphi(k)} \\ Andrew Howroyd, Jul 02 2018

Formula

T(n,k) = A057731(n,k)/A000010(k).
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