Runs in coin tossing: a general approach for deriving distributions for   functionals
  We take a fresh look at the classical problem of runs in a sequence of i.i.d.\ coin tosses and derive a general identity/recursion which can be used to compute (joint) distributions of functionals of run types. This generalizes and unifies already existing approaches. We give several examples, derive asymptotics, and pose some further questions. 
Lars Holst, Takis Konstantopoulos
math.PR