How to resolve the algorithm Numbers which are the cube roots of the product of their proper divisors step by step in the C# programming language

Published on 12 May 2024 09:40 PM

How to resolve the algorithm Numbers which are the cube roots of the product of their proper divisors step by step in the C# programming language

Table of Contents

Problem Statement

Consider the number 24. Its proper divisors are: 1, 2, 3, 4, 6, 8 and 12. Their product is 13,824 and the cube root of this is 24. So 24 satisfies the definition in the task title. Compute and show here the first 50 positive integers which are the cube roots of the product of their proper divisors. Also show the 500th and 5,000th such numbers. Compute and show the 50,000th such number. OEIS considers 1 to be the first number in this sequence even though, strictly speaking, it has no proper divisors. Please therefore do likewise.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Numbers which are the cube roots of the product of their proper divisors step by step in the C# programming language

The provided C# code determines whether a given positive integer n has exactly four or eight distinct positive divisors, including 1 and n itself. If n satisfies this condition, it then checks if n is the cube root of the product of all its proper divisors (divisors excluding n). The program continues this process until it finds the first 50 such numbers and prints them. Here's a detailed explanation of the code:

  • The dc8 function takes an unsigned 32-bit integer n as an argument. It calculates the number of distinct positive divisors of n by grouping together consecutive powers of 2, 3, and other prime factors. It returns true if n has exactly four or eight distinct positive divisors, and false otherwise.
  • The Main method initializes variables for counting, limiting, and printing. It then enters a loop that iterates through positive integers n starting from 1.
  • For each n, it checks if n is equal to 1 or if it has exactly four or eight distinct positive divisors by calling the dc8 function. If either condition is met, it increments the count and prints n in a formatted way.
  • The loop continues until it finds the first 50 numbers that meet the specified conditions, or reaches the limit lmt. Every time the count reaches lmt, the limit is multiplied by 10 to increase the search range.
  • The program prints the first 50 numbers that satisfy the given conditions in a tabular format, with 10 numbers per line.

In summary, the code efficiently checks if a given number n has exactly four or eight distinct positive divisors and then determines if n is the cube root of the product of its proper divisors. It outputs the first 50 such numbers, providing insights into the properties of positive integers and their divisors.

Source code in the csharp programming language

using System;
class Program {

  static bool dc8(uint n) {
    uint res = 1, count, p, d;
    for ( ; (n & 1) == 0; n >>= 1) res++;
    for (count = 1; n % 3 == 0; n /= 3) count++;
    for (p = 5, d = 4; p * p <= n; p += d = 6 - d)
        for (res *= count, count = 1; n % p == 0; n /= p) count++;
    return n > 1 ? res * count == 4 : res * count == 8;
  }

  static void Main(string[] args) {
    Console.WriteLine("First 50 numbers which are the cube roots of the products of "
                      + "their proper divisors:");
    for (uint n = 1, count = 0, lmt = 500; count < 5e6; ++n) if (n == 1 || dc8(n))
        if (++count <= 50) Console.Write("{0,3}{1}",n, count % 10 == 0 ? '\n' : ' ');
        else if (count == lmt) Console.Write("{0,16:n0}th: {1:n0}\n", count, n, lmt *= 10);
  }
}


  

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