Long primes: Difference between revisions
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2430 long primes <= 64000
</pre>
=={{header|FreeBASIC}}==
<lang freebasic>' version 01-02-2019
' compile with: fbc -s console
Dim Shared As UByte prime()
Sub find_primes(n As UInteger)
ReDim prime(n)
Dim As UInteger i, k
' need only to consider odd primes, 2 has no repetion
For i = 3 To n Step 2
If prime(i) = 0 Then
For k = i * i To n Step i + i
prime(k) = 1
Next
End If
Next
End Sub
Function find_period(p As UInteger) As UInteger
' finds period for every positive number
Dim As UInteger period, r = 1
Do
r = (r * 10) Mod p
period += 1
If r <= 1 Then Return period
Loop
End Function
' ------=< MAIN >=------
#Define max 64000
Dim As UInteger p = 3, n1 = 3, n2 = 500, i, n50, count
find_primes(max)
Print "Long primes upto 500 are ";
For i = n1 To n2 Step 2
If prime(i) = 0 Then
If i -1 = find_period(i) Then
If n50 <= 50 Then
Print Str(i); " ";
End If
count += 1
End If
End If
Next
Print : Print
Do
Print "There are "; Str(count); " long primes upto "; Str(n2)
n1 = n2 +1
n2 += n2
If n1 > max Then Exit Do
For i = n1 To n2 Step 2
If prime(i) = 0 Then
If i -1 = find_period(i) Then
count += 1
End If
End If
Next
Loop
' empty keyboard buffer
While Inkey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End</lang>
{{out}}
<pre>Long primes upto 500 are 7 17 19 23 29 47 59 61 97 109 113 131 149 167 179 181 193 223 229 233 257 263 269 313 337 367 379 383 389 419 433 461 487 491 499
There are 35 long primes upto 500
There are 60 long primes upto 1000
There are 116 long primes upto 2000
There are 218 long primes upto 4000
There are 390 long primes upto 8000
There are 716 long primes upto 16000
There are 1300 long primes upto 32000
There are 2430 long primes upto 64000</pre>
=={{header|Go}}==
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