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.

Previous Showing 11-20 of 20 results.

A173397 Partial sums of A000019.

Original entry on oeis.org

1, 2, 4, 6, 11, 15, 22, 29, 40, 49, 57, 63, 72, 76, 82, 104, 114, 118, 126, 130, 139, 143, 150, 155, 183, 190, 205, 219, 227, 231, 243, 250, 254, 256, 262, 284, 295, 299, 301, 309, 319, 323, 333, 337, 346, 348, 354, 358, 398, 407, 409, 412, 420, 424, 432, 441
Offset: 1

Views

Author

Jonathan Vos Post, Feb 17 2010

Keywords

Comments

Partial sums of number of primitive permutation groups of degree n. The subsequence of primes in this partial sum begins: 2, 11, 29, 139, 227, 337, 409, 463, 563, 593, 821, 853, 881 (and other powers include 243). The subsequence of squares in this partial sum begins: 1, 4, 49, 256, 441, 576.

Crossrefs

Programs

Formula

a(n) = Sum_{i=1..n} A000019(i).

A174511 The number of isomorphism classes of subgroups of the symmetric group S_n.

Original entry on oeis.org

1, 2, 4, 9, 16, 29, 55, 137, 241, 453, 894, 2065, 3845
Offset: 1

Views

Author

W. Edwin Clark, Nov 28 2010

Keywords

Comments

Two subgroups are considered to be isomorphic here if they are isomorphic as abstract groups, not as permutation groups. - N. J. A. Sloane, Nov 28 2010

Examples

			a(3) = 4 since S_3 contains up to isomorphism exactly one subgroup of each of the orders 1,2,3,6.
		

Crossrefs

Programs

  • GAP
    a:=[];
    for n in [1,2,3,4,5,6,7,8,9,10] do
      G:=SymmetricGroup(n);
      R:=ConjugacyClassesSubgroups(G);
      RR:=ListX(R,Representative);
      T:=[RR[1]];
      for g in RR do
        flag:=false;
        for h in T do
          if IsomorphismGroups(g,h)<>fail then
            flag:=true;
            break;
          fi;
        od;
        if flag=false then Add(T,g); fi;
      od;
      Add(a,Size(T));
    od;
    Print(a,"\n");

Extensions

a(11) and a(12) from Stephen A. Silver, Feb 24 2013
a(13) (as calculated by Jack Schmidt) from L. Edson Jeffery, May 26 2013

A343592 Number of symmetry types of digraphs with n nodes.

Original entry on oeis.org

1, 2, 4, 9, 14, 36
Offset: 1

Views

Author

Peter Dolland, Apr 21 2021

Keywords

Comments

The symmetry type of a digraph is determined by its automorphism group. It is a permutation group on the nodes set, and therefore a subgroup of the symmetric group Sn. The total number of these is determined by A000638. But not all of them occur as an automorphism group of a digraph.

Examples

			The four symmetry types of the digraphs with 3 nodes are represented by:
1.) {}, the empty graph, has together with the full graph the automorphism group S_3 (as subgroup of S_3) as symmetry type.
2.) {(1,2)} has together with 6 other digraphs the trivial automorphism group {id} as symmetry type. This digraph class is called asymmetric. Their values are given by A051504.
3.) {(1,2),(2,1)} has together with 5 other digraphs the automorphism group containing id and a transposition (so it is C_2 as the subgroup of S_3) as symmetry type.
4.) {(1,2),(2,3),(3,1)} has as the only digraph with three nodes the automorphism group C_3 as symmetry type. As a consequence it has to be self-complementary.
The total of the sizes of the symmetry type classes yields the number of digraphs A000273. Here: 2+7+6+1 = 16 = A000273(3).
Note, that for n > 3 there may be different symmetry types with isomorphic automorphism groups. For n=4 both {(1,2)} and {(1,2),(3,4)} have C_2 as automorphism group, but they are different as permutation group.
		

Crossrefs

A091070 Number of automorphism groups of partial orders on n points.

Original entry on oeis.org

1, 1, 2, 3, 6, 8, 16, 21, 41, 57, 103, 140, 276
Offset: 0

Views

Author

Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004

Keywords

Examples

			a(3)=3 because of the 5 partial orders on 3 points, 2 have trivial automorphism group, 2 have an automorphism of order 2 and one has the full symmetric group as its automorphism group; thus 3 different (conjugacy classes of) subgroups occur.
		

Crossrefs

Cf. A000638 (subgroups of the symmetric group), A000112 (partial orders).

A141034 Rank of the unit group of the Burnside ring of the symmetric group on n points.

Original entry on oeis.org

1, 2, 3, 6, 10, 23, 34, 67, 110, 205, 320, 660
Offset: 1

Views

Author

Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jul 30 2008

Keywords

References

  • Boltje, Robert and Pfeiffer, Goetz, An algorithm for the unit group of the Burnside ring of a finite group. Groups St. Andrews 2005. Vol. 1, pp. 230-236, London Math. Soc. Lecture Note Ser., 339, Cambridge Univ. Press, Cambridge, 2007.

Crossrefs

Cf. A000638.

A215651 Number of transformation semigroups acting on n points (counting conjugates as one), i.e., the number of subsemigroups of the full transformation semigroup T_n.

Original entry on oeis.org

1, 2, 8, 283, 132069776
Offset: 0

Views

Author

Attila Egri-Nagy, Aug 19 2012

Keywords

Comments

The semigroup analog of A000638.
We apply the categorical viewpoint and consider the empty set as a semigroup.

Crossrefs

Programs

  • GAP
    ################################################################################
    # GAP 4.5 function calculating the conjugacy classes of a set of subsemigrops.
    # (C) 2012 Attila Egri-Nagy www.egri-nagy.hu
    # GAP can be obtained from www.gap-system.org
    ################################################################################
    # Input: list of subsemigroups of a transformation semigroup,
    #        automorphism group of the semigroup
    # Output: list of conjugacy classes
    ConjugacyClassesSubsemigroups := function(subsemigroups, G)
    local ssg, #subsemigroup
          ccl, #conjugacy class
          ccls; #result: all conjugacy classes
      ccls := [];
      for ssg in subsemigroups do
        #we check whether the subsemigroup is already in a conjugacy class
        if not ForAny(ccls, x -> ssg in x) then
          #conjugating by all group elements
          ccl := DuplicateFreeList(
                         List(G,
                              g -> AsSortedList(List(ssg, t-> t^g))));
          Add(ccls, ccl);
        fi;
      od;
      return ccls;
    end;

Extensions

a(4) moved from a comment by Attila Egri-Nagy, Jan 09 2014 to data by Andrey Zabolotskiy, Mar 25 2021

A347007 Number of cycle types of permutation groups with degree n.

Original entry on oeis.org

1, 1, 2, 4, 11, 19, 55, 93, 285, 535, 1514, 2934
Offset: 0

Views

Author

Peter Dolland, Aug 10 2021

Keywords

Comments

A000638 gives the number of permutation groups of degree n. Each permutation group is assigned a cumulative cycle type resulting from the cycle types of its member permutations.

Examples

			The 4 cycle types of the 4 permutation groups with degree 3 may be represented by arrays of length 3 (the number of partitions of 3, A000041(3)), indicating the quantity of member permutations, whose cycle type yields a specific partition of n. The partitions are listed in graded lexicographical ordering (see A193073), here (1^3), (2,1), (3):
   1. [1, 0, 0]
   2. [1, 1, 0]
   3. [1, 0, 2]
   4. [1, 3, 2]
The cycle types belong to the permutation groups {id}, C2, C3, and S3 (all subgroups of S3).
Note: For degree n < 6 all permutation groups have different cycle types, so a(n) = A000638(n). For n = 6 there are exactly two permutation groups with the same cycle type (namely [1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0], both groups isomorphic with C2^2), so a(6) = 55 = A000638(6) - 1.
		

Crossrefs

Cf. A000638.

Programs

  • GAP
    # GAP 4.11.1
    n := 9;;
    G := SymmetricGroup(n);
    cc := ConjugacyClasses(G);;
    sub := ConjugacyClassesSubgroups(G);;
    rep := List(sub, Representative);;
    ctlst := List( rep, x-> List( cc, c-> Size( Intersection( x, c))));;
    Size( AsDuplicateFreeList( ctlst));

A091071 Number of normalizers of subgroups of the symmetric group on n points.

Original entry on oeis.org

1, 1, 1, 2, 4, 5, 12, 19, 42, 72, 127, 196, 500
Offset: 0

Views

Author

Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004

Keywords

Examples

			a(3)=2 because of the 4 (conjugacy classes of) subgroups of Sym(3) only 2 (Sym(2) and Sym(3)) are normalizers of subgroups.
		

References

  • G. Pfeiffer, Counting Transitive Relations, preprint, 2004.

Crossrefs

Cf. A000638 (subgroups of Sym(n)), A091070 (stabilizers of partial orders).

A174201 Partial sums of A141034.

Original entry on oeis.org

1, 3, 6, 12, 22, 45, 79, 146, 256, 461, 781, 1441
Offset: 1

Views

Author

Jonathan Vos Post, Mar 11 2010

Keywords

Comments

Partial sums of rank of the unit group of the Burnside ring of the symmetric group on n points. The underlying sequence includes the primes 2, 3, 23, 67; the subsequence of prime values in this partial sum begins: 3, 79, 461.

Crossrefs

Formula

a(n) = SUM[i=1..n] A141034(i).

A269890 Number of conjugacy classes of subgroups of the hyperoctahedral group.

Original entry on oeis.org

2, 8, 33, 193, 953, 7440, 55200, 627187, 7510549
Offset: 1

Views

Author

Martin Rubey, Mar 07 2016

Keywords

Crossrefs

Cf. A000638.

Programs

  • GAP
    Length(ConjugacyClassesSubgroups(CoxeterGroup( "B", n )));
    
  • Magma
    [#Subgroups(CoxeterGroup("B" cat IntegerToString(n))) : n in [1..9]];  // Robin Visser, Aug 09 2023

Extensions

a(6)-a(9) from Robin Visser, Aug 09 2023
Previous Showing 11-20 of 20 results.