and use it to directly calculate mod(13^271,162653);

Hi Jerry. Just two cents. (I'm missing some of the threads here)
In math programs, mod(13^271,162653) is usually done more efficiently via a
number theory algorithm that usually goes by the name "PowerMod."

Hence:
PowerMod[13, 271, 162653]

102308

For the op, the vba algorithm usually follows Equiangular's code, where the
'p term is represented in base two. This allows vba to work with very large
numbers. (above 15 if you wish, although the code is a little tricky)

In Vba:

n=123456789012346

?PowerMod(n,n+1,n+2)
30910517478724

--
Dana DeLouis



"Jerry W. Lewis" wrote in message
...
Maple and Maxima (both symbolic math programs with unlimited precision)
plus
Equiangular's VBA code all agree that mod(13^271,162653) is 102308.

Jerry

"Joel" wrote:

I still trying to determine the correct answer. I fixed some problems
with
my code and getting the answer 59026. Did anybody else get the answer
that
Jerry got 102308

Sub largemultiply()
Dim MyTotal As String

MyTotal = "13"
For i = 1 To 270
MyTotal = Multiply(MyTotal, "13")
Next i

Remainder = Divide(MyTotal, "162653#")
End Sub

Function Multiply(parm1 As String, parm2 As String) As String

Multiply = ""

For i = 0 To (Len(parm2) - 1)
carry# = 0
mychar2 = Mid(parm2, Len(parm2) - i, 1)
total = ""
For j = 0 To (Len(parm1) - 1)
mychar1 = Mid(parm1, Len(parm1) - j, 1)

prod = (Val(mychar1) * Val(mychar2)) + carry
carry = Int(prod / 10)
Remainder# = prod Mod 10
total = Trim(CStr(Remainder)) & total
Next j
If Multiply = "" Then
If carry = 0 Then
Multiply = total
Else
Multiply = Trim(CStr(carry)) & total
End If
Else
Multiply = Add(Multiply, total, i)
End If
Next i

End Function
Function Add(Multiply, total, shift)

carry = 0
If shift 0 Then
Add = Right(Multiply, shift)
Else
Add = ""
End If
loops = Len(total)
If (Len(Multiply) - shift) loops Then
loops = Len(Multiply) - shift
End If
For i = 0 To loops - 1
If Len(Multiply) - shift i Then
add1 = Val(Mid(Multiply, Len(Multiply) - (i + shift), 1))
Else
add1 = 0
End If
add2 = Val(Mid(total, Len(total) - i, 1))
Sum# = add1 + add2 + carry
carry = Int(Sum / 10)
bit = Sum Mod 10
Add = bit & Add
Next i
If carry < 0 Then
Add = carry & Add
End If
End Function

Function Divide(Quotent, Divisor)
Dim Remainder As Long

NDivisor = Val(Divisor)
NewQuotent = Val(Left(Quotent, Len(Divisor)))
loops = (Len(Quotent) - Len(Divisor))
For i = 0 To (loops - 1)
Remainder = NewQuotent Mod NDivisor
If i < loops Then
Newbit = Mid(Quotent, i + Len(Divisor) + 1, 1)
NewQuotent = (Remainder * 10) + Val(Newbit)
End If
Next i
Divide = Remainder
End Function

"Niek Otten" wrote:

Very interesting discussions!
But I've hardly seen Diogo (the OP) again.
My question: What would one need such a calculation for?

--
Kind regards,

Niek Otten
Microsoft MVP - Excel

"Diogo" wrote in message
...
| Need to calculate via Excel:
|
| mod(13^271;162653)
|
| Any thoughts????
|
| Thanks