According to
the liner notes, Niven received an undergraduate degree in
mathematics. Mostly the degree has only apparently inspired his
titles (note also the book called "The Integral Trees") without
noticeably affecting the content. The story Convergent Series,
however, has at least some of the flavor of mathematics (though I
think it would more appropriately be titled "Convergent Sequence".)
Contributed by
Ron Wax
"Niven's Convergent Series takes a standard plot of a young man who
has sold his soul but introduces a converging sequence to beat the demonic fiend at the
game. He turns the ages old horror story into a comedic escape. 
This story appears in the Niven collection of the same name and also appears
in Rucker's "Mathenauts" collection.
Contributed by
Jimbo Jones
Niven is famous for actually doing the math to figure out that a large structure (Ringworld) would require a greater tensile strength than ordinary matter can provide. (He's almost equally famous for going back and writing a sequel to fix the problem when a bunch of MIT students did more calculations and determined that the Ringworld's orbit would be unstable.)

