Created
October 22, 2018 23:01
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Ordering of finite groups by the sum of orders of their elements
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# Code for https://math.stackexchange.com/q/2933753/ | |
TestOneOrder:=function(n) | |
# find the smallest example among the groups of order n | |
local s,i,m,d,x; | |
# Calculate lists of sums of element orders. | |
# Avoid using AllSmallGroups(n) which potentially may be very large | |
s := List([1..NrSmallGroups(n)],i->Sum(List(SmallGroup(n,i),Order))); | |
if Length(Set(s))=NrSmallGroups(n) then | |
# Sum of element orders uniquely defines each group | |
return fail; | |
else | |
# There are duplicates - find them first | |
d := Filtered( Collected(s), x -> x[2] > 1 ); | |
# Find the minimal possible value of the sum of element orders | |
m := Minimum( List( d, x-> x[1] ) ); | |
# Find positions of m in the list | |
# Return the list of group IDs | |
return List( Positions(s,m), x -> [n,x] ); | |
fi; | |
end; | |
FindSmallestPair:=function(n) | |
# check all groups of order up to n | |
local i, res; | |
for i in [1..n] do | |
# \r at the end of the print returns to the beginning of the line | |
Print("Checking groups of order ", i, "\r"); | |
res := TestOneOrder(i); | |
if res<>fail then | |
# print new line before displaying the output | |
Print("\n"); | |
return res; | |
fi; | |
od; | |
return fail; | |
end; |
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