Question

How to print the first 25 abundant numbers in C++

Answer 1

#include <iostream>

// abundant number = sum of proper divisors > number
 
unsigned SumNumberProperDivisors(const unsigned num) {
    unsigned sum = 1;
     
    for (unsigned i = 2, j; i * i <= num; i++)
        if (num % i == 0)
            sum += i + (i == (j = num / i) ? 0 : j);
     
    return sum;
}
     
int main()
{
    for (unsigned num = 1, i = 0; i < 25; num++) {
        if (SumNumberProperDivisors(num) > num) {
            std::cout << ++i << " " << num << "\n";
        }
    }
}
 

 
 
/*
run:
 
1 12
2 18
3 20
4 24
5 30
6 36
7 40
8 42
9 48
10 54
11 56
12 60
13 66
14 70
15 72
16 78
17 80
18 84
19 88
20 90
21 96
22 100
23 102
24 104
25 108
 
*/

 

 

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