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:

def s(n): reduce range(1; n+1) as $k (0; . + 1/($k * $k) );

s(1000)

def summation(s): reduce s as $k (0; . + $k);

summation( range(1; 1001) | (1/(. * .) ) )