Perfect numbers–that is, positive integers that are the sum of their proper positive divisors–had fascinated mathematicians since the days of the great Greek mathematician Nicomachus. Only four were known in those days, and relatively few have been uncovered since, none of them odd–something certain figures consider an impossibility.

In 1456, Abd al-Nitypt, an astronomer in the court of Mehmed II at Constantinople, discovered and proved the existence of a fifth perfect number, 33,550,336. He further set forth a complex formula for identifying further perfect numbers, a refinement of Euclid’s formula, and identified a list of values for n which he claimed would, when applied to his formula, reveal all odd perfect numbers between 0 and 10^1500.

This list, the Nitypt Numbers, was eventually lost in the quagmire of the Ottoman archives. They, alongside Fermat’s Last Theorem, were long regarded as some of the most tantalizing mysteries in mathematics.

And Harvery was staring at a copy in al-Nitypt’s own flowing calligraphy.