Nice! But the pedant in me feels compelled to point out that for a 35% increase in length, this obfu can be made significantly more timeefficient:
$m=250;print 2;for($b=3;$b<=$m;$b+=2){if(!$d[$a]){for($a=$b*$b;$a<=$m;
+$a+=$b){$c[$a]=1}}print",$b"}
The speed increase is negligible for low values of $m, but for large value it becomes significant (e.g. an increase of nearly 8 times in speed for $m equal to ten million):
But note that this version is still inefficient. See johngg’s recent post: Re^3: Number functions I have lying around, which saves on (1) cpu time by iterating only up to sqrt($m), and (2) memory by storing the sieve in a bit vector.
Hope this is of interest,
