Anonymous user
Emirp primes: Difference between revisions
→{{header|Phix}}
Line 2,688:
emirp 10000: 938033
</pre>
=={{header|PHP}}==
<lang PHP><?php
function is_prime($n) {
if ($n <= 3) {
return $n > 1;
} elseif (($n % 2 == 0) or ($n % 3 == 0)) {
return false;
}
$i = 5;
while ($i * $i <= $n) {
if ($n % $i == 0) {
return false;
}
$i += 2;
if ($n % $i == 0) {
return false;
}
$i += 4;
}
return true;
}
function is_emirp($n) {
$r = (int) strrev((string) $n);
return (($r != $n) and is_prime($r) and is_prime($n));
}
$c = $x = 0;
$first20 = $between = '';
do {
$x++;
if (is_emirp($x)) {
$c++;
if ($c <= 20) {
$first20 .= $x . ' ';
}
if (7700 <= $x and $x <= 8000) {
$between .= $x . ' ';
}
}
} while ($c < 10000);
echo
'First twenty emirps :', PHP_EOL, $first20, PHP_EOL,
'Emirps between 7,700 and 8,000 :', PHP_EOL, $between, PHP_EOL,
'The 10,000th emirp :', PHP_EOL, $x, PHP_EOL;</lang>
{{out}}
<pre>First twenty emirps :
13 17 31 37 71 73 79 97 107 113 149 157 167 179 199 311 337 347 359 389
Emirps between 7,700 and 8,000 :
7717 7757 7817 7841 7867 7879 7901 7927 7949 7951 7963
The 10,000th emirp :
948349</pre>
=={{header|PicoLisp}}==
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