combinacions racionals

(5/6k) = 1·(1/2k) + 1·(1/3k)
( (2n+1)/(n^{2}+n)k  ) = 1·(1/nk) + 1·(1/(n+1)k)


(3/4k) = 1·(1/2k) + 1·(1/4k)
( (m+1)/(m·n)k  ) = 1·(1/nk) + 1·(1/(m·n)k)