Finding primes
Hi all,
I need a formula or function that when I input a number then it will return that prime. For example if I input 100 then I will get the 100th prime number. Your assistance would be much appreciated. D |
Finding primes
http://support.microsoft.com/?kbid=202782
-- Gary''s Student - gsnu200814 "Dave" wrote: Hi all, I need a formula or function that when I input a number then it will return that prime. For example if I input 100 then I will get the 100th prime number. Your assistance would be much appreciated. D |
Finding primes
Hi,
Thanks for that. I was a bit suspicious when the site gave an incorrect definition of a prime number and while I don't fully understand the code when I ran it it gave an incorrect answer. d "Gary''s Student" wrote: http://support.microsoft.com/?kbid=202782 -- Gary''s Student - gsnu200814 "Dave" wrote: Hi all, I need a formula or function that when I input a number then it will return that prime. For example if I input 100 then I will get the 100th prime number. Your assistance would be much appreciated. D |
Finding primes
Dave,
Why am I not surprised that the Microsoft website incorrectly defines a prime number and then goes on to provide code that confirms the lack of understanding. Perhaps you should submit as a suggestion to MS that it corrects its site. In the meantime try this. Alt+F11 to open VB editor. Right click 'This Workbook' and insert module and paste the code below in. With a number in A1 call with =nthprime(A1) With 100 in a1 it will return the 100th prime. It starts getting a bit slow with large numbers but it's the fastest way I know. Function NthPrime(PrimeRequired As Long) As Long Dim i As Long If PrimeRequired 0 Then For x = 2 To 100000000 If (x < 2 And x Mod 2 = 0) Or x < Int(x) Then GoTo 100 For i = 3 To Sqr(x) Step 2 If x Mod i = 0 Then GoTo 100 Next foundprime = foundprime + 1 If foundprime = PrimeRequired Then NthPrime = x Exit Function 100 End If Next On Error GoTo 0 End If End Function Mike "Dave" wrote: Hi, Thanks for that. I was a bit suspicious when the site gave an incorrect definition of a prime number and while I don't fully understand the code when I ran it it gave an incorrect answer. d "Gary''s Student" wrote: http://support.microsoft.com/?kbid=202782 -- Gary''s Student - gsnu200814 "Dave" wrote: Hi all, I need a formula or function that when I input a number then it will return that prime. For example if I input 100 then I will get the 100th prime number. Your assistance would be much appreciated. D |
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