Aiuto con algoritmo per disposizioni

Imports System
Imports System.Collections
Imports System.Collections.Generic

Public Class Generator
    Private a As String
    Private n As Integer

    Public Sub New(ByVal a As String, ByVal n As Integer)
        Me.a = a
        Me.n = n
    End Sub

    Public Function getVariations() As List(Of String)

        Dim l As Integer = a.Length

        Dim permutations As Integer = CInt(System.Math.Pow(l, n))
        Dim table As Char()() = New Char(permutations - 1)() {}
        For i As Integer = 0 To permutations - 1
            table(i) = New Char(n - 1) {}
        Next
        For x As Integer = 0 To n - 1

            Dim t2 As Integer = CInt(System.Math.Pow(l, x))
            Dim p1 As Integer = 0
            While p1 < permutations
                For al As Integer = 0 To l - 1
                    For p2 As Integer = 0 To t2 - 1
                        table(p1)(x) = a(al)
                        p1 += 1
                    Next
                Next
            End While
        Next
        Dim result As New List(Of String)()

        For Each permutation As Char() In table
            result.Add(New String(permutation))
        Next
        Return result
    End Function
End Class

   Dim mioThread As Thread

.....
        mioThread = New Thread(AddressOf OperazionePesante)
        mioThread.Priority = ThreadPriority.Lowest
        mioThread.Start()
.....
    

    Private Sub OperazionePesante()
    .......operazioni di calcolo.....
    End Sub

        mioThread.Abort()