The title is a pun relating the operation from calculus (the definite
integral of a function) to the controversial attempt to solve many of the
problems of race relations in America (the integration of the schools).
A summary of the plot can be found here, but
they make no mention of the mathematical aspect.
One
character's interest in the definite integral is a running theme throughout
the book and also the source of metaphors. For example, he notes that the
vertical lines often drawn on the graph during integration to represent the Riemann sum
appear
to be like prison bars...prison bars which become infinitely close
preventing any chance of escape.
This was originally published in the Saturday Evening Post in
December 1964 and can now be found in the collection Slow
Learner.
Contributed by
Will Macfarlane
"This is Pynchon's most successful short story, far outstripping in quality the publishedasanovel "The Crying of Lot 49". The mathematical aspects of the story are small but pervasive  Pynchon uses mathematical concepts as effective tools for metaphor throughout the story (and most of his other works). One of the better short stories in the world." 
