Function CorputBaseb(b As Long, N As Long) As Double
'   Returns the equivalent first van der Corput sequence number (used in Halton, Faure, Sobol)
'   b is the base X
'   n is the number to be transformed

    Dim c As Double, ib As Double
    Dim i As Long, n1 As Long, n2 As Long
    n1 = N
    c = 0
    ib = 1 / b
    Do While n1 > 0
        n2 = Int(n1 / b)
        i = n1 - n2 * b
        c = c + ib * i
        ib = ib / b
        n1 = n2
    Loop
    CorputBaseb = c
End Function