Const maxBase = 36 ' o 62
Function isPrime(Byval ValorEval As Integer) As Boolean
    If ValorEval < 2 Then Return False
    If ValorEval Mod 2 = 0 Then Return ValorEval = 2
    If ValorEval Mod 3 = 0 Then Return ValorEval = 3
    Dim d As Integer = 5
    While d * d <= ValorEval
        If ValorEval Mod d = 0 Then Return False Else d += 2
    Wend
    Return True
End Function
Function maxval(arr() As Integer) As Integer
    Dim As Integer max_value = arr(0)
    For i As Integer = 1 To Ubound(arr)
        If arr(i) > max_value Then max_value = arr(i)
    Next
    Return max_value
End Function
Function join(arr() As Integer, delimiter As String) As String
    Dim As String result = ""
    For i As Integer = 0 To Ubound(arr)
        result &= Str(arr(i))
        If i < Ubound(arr) Then result &= delimiter
    Next
    Return result
End Function

Function evalPoly(x As Integer, p() As Integer) As Integer
    Dim result As Integer = 0
    For y As Integer = 0 To Ubound(p)
        result = result * x + p(y)
    Next
    Return result
End Function

Function stringify(digits() As Integer) As String
    Dim res As String
    For i As Integer = 0 To Ubound(digits)
        Dim di As Integer = digits(i)
        res &= Chr(Iif(di <= 9, di + Asc("0"), Iif(di < 36, di + Asc("A") - 10, di + Asc("a") - 36)))
    Next
    Return res
End Function

Sub maxPrimeVases(ndig As Integer, maxVase As Integer)
    Dim As Double t0 = Timer
    Dim As String maxPrimeBases()
    Dim As Integer digits(ndig - 1)
    Dim As Integer maxlen = 0
    Dim As Integer limit = 10 ^ ndig
    Dim As Integer maxDigit = maxBase
    If ndig > 1 Then digits(0) = 1
    Do
        For i As Integer = Ubound(digits) To 0 Step -1
            Dim As Integer di = digits(i) + 1
            If di < maxDigit Then
                digits(i) = di
                Exit For
            Else
                digits(i) = 0
            End If
        Next
        Dim As Integer minBase = maxval(digits()) + 1
        Dim As Integer maxPoss = maxBase - minBase + 1
        If minBase = 1 Then Exit Do
        Dim As Integer bases()
        For base_ As Integer = minBase To maxBase
            If isPrime(evalPoly(base_, digits())) Then
                Redim Preserve bases(Ubound(bases) + 1)
                bases(Ubound(bases)) = base_
            Else
                maxPoss -= 1
                If maxPoss < maxlen Then Exit For
            End If
        Next
        Dim As Integer l = Ubound(bases) + 1
        If l > maxlen Then
            maxlen = l
            maxDigit = maxBase - maxlen
            Redim maxPrimeBases(0)
        End If
        If l = maxlen Then
            Redim Preserve maxPrimeBases(Ubound(maxPrimeBases) + 1)
            maxPrimeBases(Ubound(maxPrimeBases)) = Chr(10) & stringify(digits()) & " => " & join(bases(), ", ")
        End If
    Loop
    Print Using "# character strings which are prime in most bases: ## (#.##s):"; ndig; maxlen; Timer - t0;
    For i As Integer = 0 To Ubound(maxPrimeBases)
        Print maxPrimeBases(i);
    Next
    Print Chr(10)
End Sub

For n As Integer = 1 To Iif(maxBase > 36, 4, 6)
    maxPrimeVases(n, maxBase)
Next n

Sleep