Task: Ludic numbers
C#: using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        Console.WriteLine("First 25 ludic numbers:");
        Console.WriteLine(string.Join(", ", LudicNumbers(150).Take(25)));
        Console.WriteLine();
        
        Console.WriteLine($"There are {LudicNumbers(1001).Count()} ludic numbers below 1000");
        Console.WriteLine();
        
        foreach (var ludic in LudicNumbers(22000).Skip(1999).Take(6)
                .Select((n, i) => $"#{i+2000} = {n}")) {
            Console.WriteLine(ludic);
        }
        Console.WriteLine();
        
        Console.WriteLine("Triplets below 250:");
        var queue = new Queue<int>(5);
        foreach (int x in LudicNumbers(255)) {
            if (queue.Count == 5) queue.Dequeue();
            queue.Enqueue(x);
            if (x - 6 < 250 && queue.Contains(x - 6) && queue.Contains(x - 4)) {
                Console.WriteLine($"{x-6}, {x-4}, {x}");
            }
        }
    }
    
    public static IEnumerable<int> LudicNumbers(int limit) {
        yield return 1;
        
        
        
        Entry[] values = Enumerable.Range(0, limit + 1).Select(n => new Entry(n)).ToArray();
        for (int i = 2; i < limit; i = values[i].Next) {
            yield return values[i].N;
            int start = i;
            while (start < limit) {
                Unlink(values, start);
                for (int step = 0; step < i && start < limit; step++)
                    start = values[start].Next;
            }
        }
    }
    
    static void Unlink(Entry[] values, int index) {
        values[values[index].Prev].Next = values[index].Next;
        values[values[index].Next].Prev = values[index].Prev;
    }
    
}

struct Entry
{
    public Entry(int n) : this() {
        N = n;
        Prev = n - 1;
        Next = n + 1;
    }
    
    public int N { get; }
    public int Prev { get; set; }
    public int Next { get; set; }
}

VB: Set list = CreateObject("System.Collections.Arraylist")
Set ludic = CreateObject("System.Collections.Arraylist")


For i = 1 To 25000
	list.Add i
Next


ludic.Add list(0)
list.RemoveAt(0)


up_to_1k = 1


For j = 2 To 2005
	If list.Count > 0 Then
		If list(0) <= 1000 Then
			up_to_1k = up_to_1k + 1
		End If
		ludic.Add list(0)
	Else
		Exit For
	End If
	increment = list(0) - 1
	n = 0
	Do While n <= list.Count - 1
		list.RemoveAt(n)
		n = n + increment
	Loop
Next


WScript.StdOut.WriteLine "First 25 Ludic Numbers:"
For k = 0 To 24
	If k < 24 Then
		WScript.StdOut.Write ludic(k) & ", "
	Else
		WScript.StdOut.Write ludic(k)
	End If
Next
WScript.StdOut.WriteBlankLines(2)


WScript.StdOut.WriteLine "Ludics up to 1000: "
WScript.StdOut.WriteLine up_to_1k
WScript.StdOut.WriteBlankLines(1)


WScript.StdOut.WriteLine "The 2000th - 2005th Ludic Numbers:"
For k = 1999 To 2004
	If k < 2004 Then
		WScript.StdOut.Write ludic(k) & ", "
	Else
		WScript.StdOut.Write ludic(k)
	End If
Next
WScript.StdOut.WriteBlankLines(2)


WScript.StdOut.WriteLine "Ludic Triplets up to 250: "
triplets = ""
k = 0
Do While ludic(k) + 6 <= 250
	x2 = ludic(k) + 2
	x6 = ludic(k) + 6
	If ludic.IndexOf(x2,1) > 0 And ludic.IndexOf(x6,1) > 0 Then
		triplets = triplets & ludic(k) & ", " & x2 & ", " & x6 & vbCrLf
	End If
	k = k + 1
Loop
WScript.StdOut.WriteLine triplets