Wieferich primes: Difference between revisions
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3511
</pre>
=={{header|C#}}==
{{trans|Java}}
<lang csharp>using System;
using System.Collections.Generic;
using System.Linq;
namespace WieferichPrimes {
class Program {
static long ModPow(long @base, long exp, long mod) {
if (mod == 1) {
return 0;
}
long result = 1;
@base %= mod;
for (; exp > 0; exp >>= 1) {
if ((exp & 1) == 1) {
result = (result * @base) % mod;
}
@base = (@base * @base) % mod;
}
return result;
}
static bool[] PrimeSieve(int limit) {
bool[] sieve = Enumerable.Repeat(true, limit).ToArray();
if (limit > 0) {
sieve[0] = false;
}
if (limit > 1) {
sieve[1] = false;
}
for (int i = 4; i < limit; i += 2) {
sieve[i] = false;
}
for (int p = 3; ; p += 2) {
int q = p * p;
if (q >= limit) {
break;
}
if (sieve[p]) {
int inc = 2 * p;
for (; q < limit; q += inc) {
sieve[q] = false;
}
}
}
return sieve;
}
static List<int> WiefreichPrimes(int limit) {
bool[] sieve = PrimeSieve(limit);
List<int> result = new List<int>();
for (int p = 2; p < limit; p++) {
if (sieve[p] && ModPow(2, p - 1, p * p) == 1) {
result.Add(p);
}
}
return result;
}
static void Main() {
const int limit = 5000;
Console.WriteLine("Wieferich primes less that {0}:", limit);
foreach (int p in WiefreichPrimes(limit)) {
Console.WriteLine(p);
}
}
}
}</lang>
{{out}}
<pre>Wieferich primes less that 5000:
1093
3511</pre>
=={{header|F_Sharp|F#}}==
Line 171 ⟶ 250:
Real: 00:00:00.004
</pre>
=={{header|Factor}}==
{{works with|Factor|0.99 2021-02-05}}
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