Wiktionary
n. (context informal English) One whose mathematical skills are so remarkable as to resemble magic.
Wikipedia
A mathemagician is a mathematician who is also a magician.
The name "mathemagician" was probably first applied to Martin Gardner, but has since been used to describe many mathematician/magicians, including Arthur T. Benjamin, Persi Diaconis, Colm Mulcahy, and Shona Jean McKay. Diaconis has suggested that the reason so many mathematicians are magicians is that "inventing a magic trick and inventing a theorem are very similar activities."
A great number of self-working mentalism tricks rely on mathematical principles. Max Maven often utilizes this type of magic in his performance.
Usage examples of "mathemagician".
Her eyes flooded: a lifetime's work that she had uncovered, explored briefly by mathemagicians before her, and she had little time in which to seek a solution that helped the Watchlands.
Yet she would have to use the spell again and again before the demons' mathemagicians shaped a ward against it.
She had seen mathemagicians die from careless assumptions in spellcasting.