Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim ilosc As Integer
        ilosc = TextBox1.Text
        Console.WriteLine(silnia2(ilosc))
    End Sub
Private Function silnia2(n2 As Integer) As Long
        If (n2 + 1) = 0 Or (n2 + 1) = 1 Then
            silnia2 = 1
        ElseIf n2 > 1 Then
            silnia2 = silnia2(n2) * (n2 + 1)
        Else
            Return Nothing
        End If
    End Function
End Class