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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4.  
  5. public class Test
  6. {
  7. 	static void Main()
  8.         {
  9.             var sum = 0L;
  10.             for (int i = 1; i <= 10000; i++)
  11.             {
  12.                 long tmp;
  13.                 if ((tmp = GetDivisorSum(i)) > i && GetDivisorSum(tmp) == i)
  14.                 {
  15.                     sum += tmp + i;
  16.                 }
  17.             }
  18.             Console.WriteLine(sum);
  19.         }
  20.  
  21.         static long GetDivisorSum(long value)
  22.         {
  23.             var prime = new List<int>();
  24.             var devisor = 2;
  25.             var given = value;
  26.             if (value <= 0)
  27.                 return 0;
  28.             if (value == 1)
  29.                 return 1;
  30.             while (value != 1)
  31.             {
  32.                 if (value % devisor == 0)
  33.                 {
  34.                     prime.Add(devisor);
  35.                     value /= devisor;
  36.                 }
  37.                 else
  38.                     devisor++;
  39.             }
  40.             return prime.GroupBy(x => x)
  41.                 .Select(x => ((long)Math.Pow(x.Key, x.Count() + 1) - 1) / (x.Key - 1))
  42.                 .Aggregate((x, y) => x * y) - given;
  43.         }
  44. }
Success #stdin #stdout 0.58s 34208KB
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https://ideone.com/ZxRvCb
language:
C# (gmcs 5.20.1)
created:
9 years ago
visibility:
public

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