func C023() (interface{}, error) {
upperLimit := 28123
numbers := map[int]bool{}
for i := 1; i < upperLimit; i++ {
numbers[i] = true
}
abundantNumbers := []int{}
for i := 2; i < upperLimit; i++ {
divisors := utils.GetDivisors(i)
sumDivisors := 0
for _, divisor := range divisors[:len(divisors)-1] {
sumDivisors += divisor
}
if sumDivisors > i {
abundantNumbers = append(abundantNumbers, i)
}
}
abundantNumbersLen := len(abundantNumbers)
for i := 0; i < abundantNumbersLen; i++ {
for j := i; j < abundantNumbersLen; j++ {
abundantNumbersSum := abundantNumbers[i] + abundantNumbers[j]
if _, found := numbers[abundantNumbersSum]; found {
numbers[abundantNumbersSum] = false
}
}
}
sumNonAbundant := 0
for number, isNotSum := range numbers {
if isNotSum {
sumNonAbundant += number
}
}
return sumNonAbundant, nil
}
func c021_d(input int) int {
divisors := utils.GetDivisors(input)
return utils.SumIntSlice(divisors) - input
}