Harmonic Number The n-th harmonic number Hn is: 1 $$ H_n = 1 + \frac 1 2 + \frac 1 3 + ... + \frac 1 n = \sum_{k=1}^n \frac 1 k $$ In Haskell: 1 harmonicNumber n = sum [ 1.0 / (fromIntegral k) | k <- [1..n] ]