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Square the GCD, get the Sum (Posted on 2023-12-13) Difficulty: 3 of 5
Find all possible triplet of positive integers (a, b, c) that satisfy this system of equations:
(GCD(a,b))^2= a+b
(GCD(b,c))^2= b+c
(GCD(c,a))^2 = c+a

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Some Thoughts computer findings Comment 1 of 1
pairs=double.empty(0,2);
for a=1:2000
  if mod(a,100)==0
    disp(a)
  end
  for b=a:2000
    if gcd(a,b)^2==a+b
      pairs(end+1,:)=[a,b];
      if a~=b
        pairs(end+1,:)=[b,a];
      end
    end
  end
end

pairs=sortrows(pairs,1);
writematrix(pairs);
clc
for aptr=1:length(pairs)
  a=pairs(aptr,1);
  b=pairs(aptr,2);
  cptr=find(pairs(:,1)==b);
  for i=1:length(cptr)
    c=pairs(cptr(i),2);
    if gcd(c,a)^2==c+a
      if a~=b && b~=c && a~=c
        flag="***";
      else
        flag=" ";
      end
      fprintf('%5d %5d %5d %s\n',a,b,c,flag)
    end
  end
end

 finds only (2,2,2)

  Posted by Charlie on 2023-12-14 08:11:43
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