Problem Statement

Compute the   nth   term of a series,   i.e. the sum of the   n   first terms of the corresponding sequence.
Informally this value, or its limit when   n   tends to infinity, is also called the sum of the series, thus the title of this task. For this task, use:

This approximates the   zeta function   for   S=2,   whose exact value is the solution of the Basel problem.

Let's start with the solution:

(scl 9)  # Calculate with 9 digits precision

(let S 0
   (for I 1000
      (inc 'S (*/ 1.0 (* I I))) )
   (prinl (round S 6)) )  # Round result to 6 digits