[walrus]

Concrete Mathematics is essentially the mathematics needed to study analysis of algorithms. From the preface:

  One of the present authors had embarked on a series of books called
  The Art of Computer Programming, and in writing the first volume he
  (DEK) had found that there were mathematical tools missing from his
  repertoire; the mathematics he needed for a thorough, well-grounded
  understanding of computer programs was quite different from what he'd
  learned as a mathematics major in college. So he introduced a new
  course, teaching what he wished somebody had taught him.

So yes, there are practical applications. And recurrences are a recurring theme, but there's more to it than just that.