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code-golf number number-theory math integer
Is this number Loeschian?
A positive integer k is a Loeschian number if
k can be expressed as i^2 + j^2 + i*j for i, j integers.
For example, the first positive Loeschian numbers are: 3 (i=j=1); 4 (i=2, j=0); 7 (i=2, j=1); 9 (i=-3, j=3); ... Note...