Function aDerivative(Byval n As Longint) As Longint
    If n < 0 Then Return -aDerivative(-n)
    If n = 0 Or n = 1 Then Return 0
    If n = 2 Then Return 1

    Dim As Longint q, d = 2
    Dim As Longint result = 1

    While d * d <= n
        If n Mod d = 0 Then
            q = n \ d
            result = q * aDerivative(d) + d * aDerivative(q)
            Exit While
        End If
        d += 1
    Wend

    Return result
End Function

'Main program
Print "Arithmetic derivatives for -99 through 100:"

Dim As Integer col, n
col = 0
For n = -99 To 100
    col += 1
    Print Using "####"; aDerivative(n);
    If col = 10 Then
        Print
        col = 0
    Else
        Print " ";
    End If
Next

'Stretch task
Print !"\n\nPowers of 10 derivatives divided by 7:"
Dim As Double m = 1
For n = 1 To 18 ' LongInt limit in FreeBASIC
    m *= 10
    Dim As Longint a = aDerivative(Clngint(m))
    Print Using "D(10^&) / 7 = &"; n; a \ 7
Next

Sleep