

A196111


Number of isomorphism classes of simple quandles of order n.


1



1, 1, 1, 3, 0, 5, 2, 3, 1, 9, 1, 11, 0, 2, 3, 15, 0, 17, 2, 2, 0, 21, 1, 10, 0, 8, 2, 27, 1, 29, 6, 0, 0, 0, 3, 35, 0, 0, 2, 39, 3, 41, 0, 3, 0, 45
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OFFSET

2,4


COMMENTS

A quandle is simple if it has more than one element, and if it has no homomorphic images other than itself or the singleton quandle. Since a simple quandle with more than two elements is connected, we have a(n) <= A181771(n), for n > 2, with equality if n is prime.
Some authors consider the quandle with one element to be simple and some do not.


LINKS

Table of n, a(n) for n=2..47.
W. E. Clark, M. Elhamdadi, M. Saito, T. Yeatman, Quandle Colorings of Knots and Applications, arXiv preprint arXiv:1312.3307, 2013
David Joyce, Simple Quandles, J. Algebra 79(2) 1982, 307318.
Leandro Vendramin, On the classification of quandles of low order, arXiv:1105.5341v1 [math.GT].
Leandro Vendramin and Matías Graña, Rig, a GAP package for racks and quandles.
Wikipedia, Racks and quandles


FORMULA

a(p) = A181771(p) = p  2, for prime p > 2.


EXAMPLE

a(2) = 1 since the quandle of order 2 is trivially simple (though not connected).


PROG

(GAP) (using the Rig package)
LoadPackage("rig");
IsSimpleQuandle:=function(q)
local g, N, gg, n;
if IsFaithful(q) = false then return false; fi;
g:=InnerGroup(q);;
if Size(Center(g))>1 then return false; fi;
N:=NormalSubgroups(g);;
gg:=DerivedSubgroup(g);;
for n in N do
if Size(n) = 1 then continue; fi;
if IsSubset(gg, n) and Size(n)<Size(gg) then return false; fi;
od;
return true;
end;;
a:=[1, 1];;
for n in [3..35] do
a[n]:=0;
for i in [1..NrSmallQuandles(n)] do
if IsSimpleQuandle(SmallQuandle(n, i)) then
a[n]:=a[n]+1;
fi;
od;
od;
List([1..35], u>a[u]);
W. Edwin Clark


CROSSREFS

Cf. A181769, A181771.
See also Index to OEIS under quandles.
Sequence in context: A130054 A187886 A236146 * A261628 A007431 A215447
Adjacent sequences: A196108 A196109 A196110 * A196112 A196113 A196114


KEYWORD

nonn,hard,more


AUTHOR

James McCarron, Oct 27 2011


EXTENSIONS

a(21) corrected by W. Edwin Clark, Dec 06 2011
a(32)a(35) added by W. Edwin Clark, Dec 06 2011
a(36)a(47) added by W. Edwin Clark, Dec 28 2014


STATUS

approved



