I believe (at least go) testcases incorrect, since for example we have pair 71145 - 67095, and if N is 7000, we should not consider both numbers, while testcase would be green only if you add 67095 but ignore 71145.

The amicable numbers are a well-studied sequecence, and a list of several of them can be found here. Technically, you could just use this list to find your result, but I encourage you to use them only for checking and testing your code. Otherwise, what's the point?

// C# using System; using System.Collections.Generic;

class Program { static int S(int n) { int sum = 1;

    for (int x = 2; x <= Math.Sqrt(n); x++)
    {
        if (n % x == 0)
        {
            sum += x + n / x;
        }
    }

    return sum;
}

static void Main()
{
    int numTestCases = int.Parse(Console.ReadLine());
    List<int> testCases = new List<int>();

    for (int i = 0; i < numTestCases; i++)
    {
        testCases.Add(int.Parse(Console.ReadLine()));
    }

    HashSet<int> result = new HashSet<int>();

    for (int x = 0; x <= testCases.Max(); x++)
    {
        if (x == S(S(x)) && x != S(x))
        {
            result.Add(x);
        }
    }

    foreach (int testCase in testCases)
    {
        Console.WriteLine(result.Where(x => x <= testCase).Sum());
    }
}

}