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 1-5 of 5 results.

A071605 Number of ordered pairs (a,b) of elements of the symmetric group S_n such that the pair a,b generates S_n.

Original entry on oeis.org

1, 3, 18, 216, 6840, 228960, 15573600, 994533120, 85232891520, 8641918252800, 1068888956889600, 155398203460684800, 26564263279602048000
Offset: 1

Views

Author

Sharon Sela (sharonsela(AT)hotmail.com), Jun 02 2002

Keywords

Comments

a(n) is an Eulerian function of S_n. - Kenneth G. Hawes, Nov 25 2019

Crossrefs

Programs

  • GAP
    a := function(n)
      local tom, mu, lens, orders, num, k;
      tom := TableOfMarks(Concatenation("S",String(n)));
      if tom = fail then tom := TableOfMarks(SymmetricGroup(n)); fi;
      mu :=  MoebiusTom(tom).mu;
      lens := LengthsTom(tom);
      orders := OrdersTom(tom);
      num := 0;
      for k in [1 .. Length(lens)] do
        if IsBound(mu[k]) then
          num := num + mu[k] * lens[k] * orders[k]^2;
        fi;
      od;
      return num;
    end; # Stephen A. Silver, Feb 20 2013

Formula

Except for n=2 (because of the "replacement") in A040175, a(n) = n! * A040175(n).
a(n) = 2 * A001691(n) for n > 2.

Extensions

a(10)-a(13) added by Stephen A. Silver, Feb 20 2013

A040173 Numerator of probability that 2 elements of S_n chosen at random (with replacement) generate S_n.

Original entry on oeis.org

1, 3, 1, 3, 19, 53, 103, 4111, 78293, 29401, 4462987, 9830941, 284397779
Offset: 1

Views

Author

Keywords

Examples

			Values for n=1,2,3,... are 1, 3/4, 1/2, 3/8, 19/40, 53/120, 103/168, 4111/6720, 78293/120960, ...
		

Crossrefs

Probability is A040173/A040174 = A040175/n!.

Extensions

a(10)-a(13) from Stephen A. Silver, Feb 21 2013

A040174 Denominator of probability that 2 elements of S_n chosen at random (with replacement) generate S_n.

Original entry on oeis.org

1, 4, 2, 8, 40, 120, 168, 6720, 120960, 44800, 6652800, 14515200, 415134720
Offset: 1

Views

Author

Keywords

Examples

			Values for n=1,2,3,... are 1, 3/4, 1/2, 3/8, 19/40, 53/120, 103/168, 4111/6720, 78293/120960, ...
		

Crossrefs

Probability is A040173/A040174 = A040175/n!.

Extensions

a(10)-a(13) from Stephen A. Silver, Feb 21 2013

A135474 A071605(n)/(n-1)!.

Original entry on oeis.org

1, 3, 9, 36, 285, 1908, 21630, 197328, 2113911, 23814810, 294557142, 3893052636, 55457566905
Offset: 1

Views

Author

N. J. A. Sloane, Feb 08 2008

Keywords

Crossrefs

Extensions

a(10)-a(13) from Stephen A. Silver, Feb 21 2013

A224539 Number of pairs of elements of the full transformational monoid T_n on {1,...,n} which generate a synchronizing monoid.

Original entry on oeis.org

1, 12, 549, 51520, 8063385, 1871446896
Offset: 1

Views

Author

N. J. A. Sloane, Apr 29 2013

Keywords

Comments

This is an analog for T_n of sequence A071605 (or A040175) for the symmetric group S_n.

References

  • P. J. Cameron, Dixon's theorem and random synchronization, Discrete Math., 313 (2013), 1233-1246. (a(1)-a(6) were computed by James Mitchell.)

Crossrefs

Showing 1-5 of 5 results.