His method relies on some fairly basic mathematics indeed, it uses another of Fermat's theorems, known as Fermat's little theorem.

ECONOMIST: Number theory

What impact did computers have on solving Fermat's theorem?

FORBES: Simon Singh says

It involves questions like Fermat's Last Theorem and the Riemann Hypothesis.

NPR: The Math Behind Pellicano's Code

However, the famous Fermat's Last Theorem tells us that if the numbers are not squared but, say, multiplied three times (cubed) then no numbers can be found that will work.

BBC: The secret of squares revealed

At Harvard (class of '72) he studied mathematics and he maintains his interest in the world of figures, socializing with math professors and even moderating a discussion about the solution of Fermat's Last Theorem.

FORBES: Polymath scion

For a comprehensive yet eminently comprehensible account of how cosmologists pieced together the history of the universe, turn to the latest book by Simon Singh, a British science writer best known for his bestselling account of the solution of Fermat's last theorem.

ECONOMIST: The quest to explain the structure of the universe