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<?php $primes = array(); for ($x = 2; $x <= 1000; $x++) { $xIsPrime = TRUE; $sqrtX = sqrt($x); foreach ($primes as $prime) if ($prime > $sqrtX || ((!($x % $prime)) && (!$xIsPrime = FALSE))) break; if ($xIsPrime) echo ($primes[] = $x) . "<br>"; }

preferences:
40.14 ms | 402 KiB | 5 Q