func Euler028(size int) int {
TRxDL := make([]int, 0, size-1)
TLxDR := make([]int, 0, size-1)
for i := 3; i <= size; i += 2 {
tr := i * i
TRxDL = append(TRxDL, tr, tr-2*(i-1))
TLxDR = append(TLxDR, tr-(i-1), tr-3*(i-1))
}
return utils.Sum(TRxDL) + utils.Sum(TLxDR) + 1
}
func Euler023(limit int) int {
abNums := []int{}
for i := 1; i < limit; i++ {
d := utils.Divisors(i)
if utils.Sum(d[:len(d)-1]) > i {
abNums = append(abNums, i)
}
}
possibleSums := make(map[int]bool)
for _, a1 := range abNums {
for _, a2 := range abNums {
if a1+a2 < limit {
possibleSums[a1+a2] = true
}
}
}
sum := 0
for i := 0; i < limit; i++ {
if !possibleSums[i] {
sum += i
}
}
return sum
}