Data update

Task/Arithmetic-numbers/C-sharp/arithmetic-numbers.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+public class ArithmeticNumbers
+{
+    public static void Main(string[] args)
+    {
+        int arithmeticCount = 0;
+        int compositeCount = 0;
+        int n = 1;
+
+        while (arithmeticCount <= 1_000_000)
+        {
+            var factors = Factors(n);
+            int sum = factors.Sum();
+            if (sum % factors.Count == 0)
+            {
+                arithmeticCount++;
+                if (factors.Count > 2)
+                {
+                    compositeCount++;
+                }
+                if (arithmeticCount <= 100)
+                {
+                    Console.Write($"{n,3}{(arithmeticCount % 10 == 0 ? "\n" : " ")}");
+                }
+                if (new[] { 1_000, 10_000, 100_000, 1_000_000 }.Contains(arithmeticCount))
+                {
+                    Console.WriteLine();
+                    Console.WriteLine($"{arithmeticCount}th arithmetic number is {n}");
+                    Console.WriteLine($"Number of composite arithmetic numbers <= {n}: {compositeCount}");
+                }
+            }
+            n++;
+        }
+    }
+
+    private static HashSet<int> Factors(int number)
+    {
+        var result = new HashSet<int> { 1, number };
+        int i = 2;
+        int j;
+        while ((j = number / i) >= i)
+        {
+            if (i * j == number)
+            {
+                result.Add(i);
+                result.Add(j);
+            }
+            i++;
+        }
+        return result;
+    }
+}