Abstract
We show that there are at most 19 integers that are not of the form $xy+yz+xz$ with $x,y,z \ge 1$. Eighteen of them are small and easily found. The remaining possibility must be greater than $10^{11}$ and cannot occur if we assume the Generalized Riemann Hypothesis.
Citation
Jonathan Borwein. Kwok-Kwong Stephen Choi. "On the representations of $xy+yz+zx$." Experiment. Math. 9 (1) 153 - 158, 2000.
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