# Problem 171: Finding numbers for which the sum of the squares of the digits is a square

![graphic](img171.gif)

For a positive integer n, let f(n) be the sum of the squares of the
digits (in base 10) of n, e.g. f(3) = 32 = 9, f(25) = 22 + 52 = 4 + 25 =
29, f(442) = 42 + 42 + 22 = 16 + 16 + 4 = 36 Find the last nine digits
of the sum of all n, 0 < n < 1020, such that f(n) is a perfect
square.