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 1-2 of 2 results.

A222029 Triangle of number of functions in a size n set for which the sequence of composition powers ends in a length k cycle.

Original entry on oeis.org

1, 1, 3, 1, 16, 9, 2, 125, 93, 32, 6, 1296, 1155, 480, 150, 24, 20, 16807, 17025, 7880, 3240, 864, 840, 262144, 292383, 145320, 71610, 24192, 26250, 720, 0, 0, 504, 0, 420, 4782969, 5752131, 3009888, 1692180, 653184, 773920, 46080, 5040, 0, 32256, 0, 26880, 0, 0, 2688
Offset: 0

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Author

Chad Brewbaker, May 14 2013

Keywords

Comments

If you take the powers of a finite function you generate a lollipop graph. This table organizes the lollipops by cycle size. The table organized by total lollipop size with the tail included is A225725.
Warning: For T(n,k) after the sixth row there are zero entries and k can be greater than n: T(7,k) = |{1=>262144, 2=>292383, 3=>145320, 4=>71610, 5=>24192, 6=>26250, 7=>720, 8=>0, 9=>0, 10=>504, 11=>0, 12=>420}|.

Examples

			T(1,1) = |{[0]}|, T(2,1) = |{[0,0],[0,1],[1,1]}|, T(2,2) = |{[0,1]}|.
Triangle starts:
       1;
       1;
       3,      1;
      16,      9,      2;
     125,     93,     32,     6;
    1296,   1155,    480,   150,    24,    20;
   16807,  17025,   7880,  3240,   864,   840;
  262144, 292383, 145320, 71610, 24192, 26250, 720, 0, 0, 504, 0, 420;
  ...
		

Crossrefs

Rows sums give A000312.
Row lengths are A000793.
Number of nonzero elements of rows give A009490.
Last elements of rows give A162682.
Main diagonal gives A290961.
Cf. A057731 (the same for permutations), A290932.

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:
    T:= n-> (p-> seq(coeff(p, x, i), i=1..degree(p)))(add(
             b(j, 1)*n^(n-j)*binomial(n-1, j-1), j=0..n)):
    seq(T(n), n=0..10);  # Alois P. Heinz, Aug 14 2017
  • 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, n}]]; T[n_]:=If[n==0, {1}, Drop[CoefficientList[Sum[b[j, 1]n^(n - j)*Binomial[n - 1, j - 1], {j, 0, n}], x], 1]]; Table[T[n], {n, 0, 10}]//Flatten (* Indranil Ghosh, Aug 17 2017 *)
  • Python
    from sympy.core.cache import cacheit
    from sympy import binomial, Symbol, lcm, factorial as f, Poly, flatten
    x=Symbol('x')
    @cacheit
    def b(n, m): return x**m if n==0 else sum([f(j - 1)*b(n - j, lcm(m, j))*binomial(n - 1, j - 1) for j in range(1, n + 1)])
    def T(n): return Poly(sum([b(j, 1)*n**(n - j)*binomial(n - 1, j - 1) for j in range(n + 1)]),x).all_coeffs()[::-1][1:]
    print([T(n) for n in range(11)]) # Indranil Ghosh, Aug 17 2017

Formula

Sum_{k=1..A000793(n)} k * T(n,k) = A290932. - Alois P. Heinz, Aug 14 2017

Extensions

T(0,1)=1 prepended by Alois P. Heinz, Aug 14 2017

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
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