Question

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

Answer 1

#include <iostream>
#include <cmath>

// abundant odd number = sum of proper divisors > number

unsigned SumOddNumberProperDivisors(const unsigned num) {
    unsigned sum = 1;
     
    for (unsigned i = 3, j; i < sqrt(num) + 1; i += 2) 
        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 += 2) {
        if (SumOddNumberProperDivisors(num) > num) {
            std::cout << ++i << " " << num << "\n";
        }
    }
}




/*
run:

1 945
2 1575
3 2205
4 2835
5 3465
6 4095
7 4725
8 5355
9 5775
10 5985
11 6435
12 6615
13 6825
14 7245
15 7425
16 7875
17 8085
18 8415
19 8505
20 8925
21 9135
22 9555
23 9765
24 10395
25 11025

*/

 

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