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<?php function get_primes7($n) { if ($n < 2) return array(); if ($n == 2) return array(2); $s = range(3, $n, 2); $mroot = sqrt($n); $half = count($s); $i = 0; $m = 3; while ($m <= $mroot) { if ($s[$i]) { $j = (int)(($m*$m - 3) / 2); $s[$j] = 0; while ($j < $half) { $s[$j] = 0; $j += $m; } } $i = $i + 1; $m = 2*$i + 3; } $res = array(2); foreach ($s as $v) { if ($v) { $res[] = $v; } } return $res; } $res = array(); for ($i = 1; $i <= 10; ++$i) { $res = get_primes7(10000); print "Found ".count($res)." prime numbers.\n"; }

preferences:
35.03 ms | 402 KiB | 5 Q