func isAmicable(s *euler.Sieve, a int) bool {
if a >= limit {
return false
}
b := s.ProperDivisorSum(a)
if b >= limit || a == b {
return false
}
c := s.ProperDivisorSum(b)
return a == c
}
func isAbundant(s *euler.Sieve, n int) bool {
return s.ProperDivisorSum(n) > n
}
