s = 1 n = 5 for k in [2..n]: s = s + k^2 s print '1^2 + 2^2 + ... + ', n^2 , '=', s
n*(n+1)*(2*n+1)/6
f=x^2 n=5 print '1^2 + 2^2 + ... +', n^2, '=', sum(f,x,1,n)