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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A293211 Triangle T(n,k) is the number of permutations on n elements with at least one k-cycle for 1 <= k <= n.

Original entry on oeis.org

1, 1, 1, 4, 3, 2, 15, 9, 8, 6, 76, 45, 40, 30, 24, 455, 285, 200, 180, 144, 120, 3186, 1995, 1400, 1260, 1008, 840, 720, 25487, 15855, 11200, 8820, 8064, 6720, 5760, 5040, 229384, 142695, 103040, 79380, 72576, 60480, 51840, 45360, 40320, 2293839, 1427895, 1030400, 793800, 653184, 604800, 518400, 453600, 403200, 362880
Offset: 1

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Author

Dennis P. Walsh, Oct 02 2017

Keywords

Comments

T(n,k) is equivalent to n! minus the number of permutations on n elements with zero k-cycles (sequence A122974).

Examples

			T(n,k) (the first 8 rows):
:     1;
:     1,     1;
:     4,     3,     2;
:    15,     9,     8,    6;
:    76,    45,    40,   30,   24;
:   455,   285,   200,  180,  144,  120;
:  3186,  1995,  1400, 1260, 1008,  840,  720;
: 25487, 15855, 11200, 8820, 8064, 6720, 5760, 5040;
  ...
T(4,3)=8 since there are exactly 8 permutations on {1,2,3,4} with at least one 3-cycle: (1)(234), (1)(243), (2)(134), (2)(143), (3)(124), (3)(142), (4)(123), and (4)(132).
		

Crossrefs

Row sums give A132961.
T(n,n) gives A000142(n-1) for n>0.
T(2n,n) gives A052145.

Programs

  • Maple
    T:=(n,k)->n!*sum((-1)^(j+1)*(1/k)^j/j!,j=1..floor(n/k)); seq(seq(T(n,k),k=1..n),n=1..10);
  • Mathematica
    Table[n!*Sum[(-1)^(j + 1)*(1/k)^j/j!, {j, Floor[n/k]}], {n, 10}, {k, n}] // Flatten (* Michael De Vlieger, Oct 02 2017 *)

Formula

T(n,k) = n! * Sum_{j=1..floor(n/k)} (-1)^(j+1)*(1/k)^j/j!.
T(n,k) = n! - A122974(n,k).
E.g.f. of column k: (1-exp(-x^k/k))/(1-x). - Alois P. Heinz, Oct 11 2017

A071007 Number of permutations in the symmetric group S_n such that the maximal cycle has length exactly 3.

Original entry on oeis.org

0, 0, 0, 2, 8, 40, 200, 980, 5152, 28448, 162080, 979000, 6179360, 40575392, 279199648, 1997406320, 14825619200, 114365751040, 912510870272, 7521873125408, 64045101880960, 561615674345600, 5067769601121920, 47023128008540992, 447820056115824128
Offset: 0

Views

Author

Sharon Sela (sharonsela(AT)hotmail.com), May 19 2002

Keywords

Comments

E.g.f.: exp( x + (x^2)/2 + (x^3)/3 ) - exp( x + (x^2)/2 ).

Crossrefs

Column k=3 of A126074.

Programs

  • Mathematica
    nn=20;Range[0,nn]!CoefficientList[Series[Exp[x+x^2/2+x^3/3]-Exp[x+x^2/2],{x,0,nn}],x]  (* Geoffrey Critzer, Jan 23 2013 *)
  • PARI
    for(n=0,25,print1(polcoeff(serlaplace(exp(x+x^2/2+x^3/3)-exp(x+x^2/2)),n)","))

Formula

a(n) = A057693(n) - A000085(n).

Extensions

More terms from Ralf Stephan, Apr 09 2003
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