Data update

Task/Blum-integer/C-sharp/blum-integer.cs

@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+
+public class BlumInteger
+{
+    public static void Main(string[] args)
+    {
+        int[] blums = new int[50];
+        int blumCount = 0;
+        Dictionary<int, int> lastDigitCounts = new Dictionary<int, int>();
+        int number = 1;
+
+        while (blumCount < 400000)
+        {
+            int prime = LeastPrimeFactor(number);
+            if (prime % 4 == 3)
+            {
+                int quotient = number / prime;
+                if (quotient != prime && IsPrimeType3(quotient))
+                {
+                    if (blumCount < 50)
+                    {
+                        blums[blumCount] = number;
+                    }
+
+                    if (!lastDigitCounts.ContainsKey(number % 10))
+                    {
+                        lastDigitCounts[number % 10] = 0;
+                    }
+                    lastDigitCounts[number % 10]++;
+
+                    blumCount++;
+                    if (blumCount == 50)
+                    {
+                        Console.WriteLine("The first 50 Blum integers:");
+                        for (int i = 0; i < 50; i++)
+                        {
+                            Console.Write($"{blums[i],3}");
+                            Console.Write((i % 10 == 9) ? Environment.NewLine : " ");
+                        }
+                        Console.WriteLine();
+                    }
+                    else if (blumCount == 26828 || blumCount % 100000 == 0)
+                    {
+                        Console.WriteLine($"The {blumCount}th Blum integer is: {number}");
+                        if (blumCount == 400000)
+                        {
+                            Console.WriteLine();
+                            Console.WriteLine("Percent distribution of the first 400000 Blum integers:");
+                            foreach (var key in lastDigitCounts.Keys)
+                            {
+                                Console.WriteLine($"    {((double)lastDigitCounts[key] / 4000):0.000}% end in {key}");
+                            }
+                        }
+                    }
+                }
+            }
+            number += (number % 5 == 3) ? 4 : 2;
+        }
+    }
+
+    private static bool IsPrimeType3(int number)
+    {
+        if (number < 2) return false;
+        if (number % 2 == 0) return number == 2;
+        if (number % 3 == 0) return number == 3;
+
+        for (int divisor = 5; divisor * divisor <= number; divisor += 2)
+        {
+            if (number % divisor == 0) return false;
+        }
+        return number % 4 == 3;
+    }
+
+    private static int LeastPrimeFactor(int number)
+    {
+        if (number == 1) return 1;
+        if (number % 2 == 0) return 2;
+        if (number % 3 == 0) return 3;
+        if (number % 5 == 0) return 5;
+
+        for (int divisor = 7; divisor * divisor <= number; divisor += 2)
+        {
+            if (number % divisor == 0) return divisor;
+        }
+        return number;
+    }
+}