"An experimental treatment for a drowning victim turns him into an incredible supergenius. Mathematics is mentioned several times in passing, and twice the supergenius explicitly uses it for his applications. But he forgets one obvious thing."

This novelette is breathtaking - perhaps the only serious attempt I've ever read at describing what a superhuman mind could be - but its focus on finding patterns and meaning in the world makes little mention of explicit mathematics.

The most notable passage, mathematically speaking, is when the protagonist decrypts in hours a file that would normally take years to a supercomputer, claiming to be using a technique for factoring large numbers he's discovered while amusing himself with number theory.

I'd say the focus is information theory rather than classic matematics. (spoiler alert) Though the evolution of the main character intelect is quite a compelling read, the key insight for me was how two equally powerful intelects, presented with the same information could diverge so wildly in their interpretations and actions, based solely in their relatives points of view of such reality (introspection for Leon, empathy for his nemesis).

Ted Chiang's Story of Your Life and Others is a mandatory read in my opinion.