ATLAS: O'Nan group O'N
Order = 460815505920.
Mult = 3.
Out = 2.
The following information is available for O'N:
Standard generators of the O'Nan group O'N are a
and b where
a has order 2,
b is in class 4A, and
ab has order 11.
Standard generators of the triple cover 3O'N are
preimages A
and B where
A has order 2,
and B has order 4.
Standard generators of the automorphism group O'N:2 are
c
and d where
c is in class 2B,
d is in class 4A, and
cd has order 22.
Standard generators of 3O'N:2 are preimages
C and D, where
D has order 4.
A pair of generators conjugate to
a, b can be obtained as
a' = (cdd)^{2}dd(cdd)^2,
b' = d.
The outer automorphism of O'N may be realised by mapping
(a,b) to (a,b^{1}).
Finding generators
To find standard generators for O'N:
 Find any element of order 20 or 28. It powers up to a 2Aelement x and a 4Aelement y.
 Find a conjugate a of x and a conjugate b of y, whose product has order 11.
This algorithm is available in computer readable format:
finder for O'N.
To find standard generators for O'N.2:
 Find any element of order 22, 30 or 38. It powers up to a 2Belement.
 Find any element of order 20, 28 or 56. This powers up to a 4Aelement, y, say.
 Find a conjugate a of x and a conjugate b of y, whose product has order 22.
This algorithm is available in computer readable format:
finder for O'N.2.
Checking generators
To check that elements x and y of O'N
are standard generators:
 Check o(x) = 2
 Check o(y) = 4
 Check o(xy) = 11
 Let z = xyxy(yy(yy)^{xyxy})^{5}
 Check o(z) = 5
 Check o([y,z]) = 1
This algorithm is available in computer readable format:
checker for O'N.
To check that elements x and y of O'N.2
are standard generators:
 Check o(x) = 2
 Check o(y) = 4
 Check o(xy) = 22
 Let z = (xyyxyx(yy(yy)^{xyyxyx})^{7})^{2}
 Check o([y,z]) = 1
This algorithm is available in computer readable format:
checker for O'N.2.
The representations of O'N available are

Dimension 154 over GF(3):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).

Dimension 342 over GF(9):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).
Kindly provided by Jürgen Müller.

Dimension 342 over GF(9):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).
Kindly provided by Jürgen Müller.

Dimension 684 over GF(3)  reducible over GF(9):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).
Kindly provided by Jürgen Müller.

Dimension 495 over GF(3):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).

Dimension 406 over GF(7):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).

Dimension 1618 over GF(7):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).

Dimension 1869 over GF(31):
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).

Permutations on 122760 points:
a and
b (Meataxe),
a and
b (Meataxe binary),
a and
b (GAP).
The representations of 3O'N available are

Dimension 153 over GF(4):
A and
B (Meataxe),
A and
B (Meataxe binary),
A and
B (GAP).

Dimension 45 over GF(7):
A and
B (Meataxe),
A and
B (Meataxe binary),
A and
B (GAP).

Dimension 45 over GF(7):
A and
B (Meataxe),
A and
B (Meataxe binary),
A and
B (GAP).

Permutations on 368280 points:
A and
B (Meataxe),
A and
B (Meataxe binary),
A and
B (GAP).
The representations of O'N:2 available are

Dimension 154 over GF(9):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Dimension 684 over GF(3):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Dimension 990 over GF(3):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Dimension 406 over GF(7):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Dimension 1618 over GF(7):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Dimension 1869 over GF(31):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).

Permutations on 245520 points:
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).
The representations of O'N:4 available are as follows.
This group is isoclinic
to O'N:2, and has structure O'N:4,
where an outer element of order 4 squares to 1.

Dimension 154 over GF(3):
c and
d (Meataxe),
c and
d (Meataxe binary),
c and
d (GAP).
The representations of 3O'N:2 available are

Dimension 306 over GF(2):
C and
D (Meataxe),
C and
D (Meataxe binary),
C and
D (GAP).

Dimension 90 over GF(7):
C and
D (Meataxe),
C and
D (Meataxe binary),
C and
D (GAP).

Permutations on 736560 points:
C and
D (Meataxe),
C and
D (Meataxe binary),
C and
D (GAP).
The maximal subgroups of O'N are
 L3(7):2, with standard generators
b^1ab,
(abb)^2b(abb)^2
.
 L3(7):2, with standard generators
bab^1,
(abb)^2bbb(abb)^2.
 J1, with standard generators
(abb)^7a(abb)^7,
(ababb)^6(ababababbababb)^4(ababb)^6
.
 4.L3(4):2, with (nonstandard) generators
[(ababb)^10,b]^14,
ababb
.
 (3^2:4 x A6).2, with generators
here.
 3^4:2^1+4.D10, with generators
here.
 L2(31), with (nonstandard) generators
(ab)^3a(ab)^3,
(ababbb)^4
.
 L2(31), with (nonstandard) generators
(abbb)^3a(abbb)^3,
(abbbab)^4
.
 4^3.L3(2), with generators
(ab)^4a(ab)^4,
(abb)^4(ababababbababb)^4(abb)^4
.
 M11, with standard generators
here.
 M11, with standard generators
here.
 A7, with generators
here.
 A7, with generators
here.
The maximal subgroups of O'N:2 are
A set of generators for the maximal cyclic subgroups of O'N can be obtained
by running this program on the standard
generators. All conjugacy classes can therefore be obtained as suitable
powers of these elements.
A set of generators for the maximal cyclic subgroups of O'N:2 can be obtained
by running this program on the standard
generators. All conjugacy classes can therefore be obtained as suitable
powers of these elements.
Problems of algebraic conjugacy are not yet dealt with.
Go to main ATLAS (version 2.0) page.
Go to sporadic groups page.
Go to old O'N page  ATLAS version 1.
Anonymous ftp access is also available.
Version 2.0 created on 7th June 2000.
Last updated 7.1.05 by SJN.
Information checked to
Level 0 on 07.06.00 by RAW.
R.A.Wilson, R.A.Parker and J.N.Bray.