note cforde In the pursuit of efficiency I have come up with a slightly different implementation: Carl1. In Carl2 I tried to optimize at the expense of a few more characters. <p> On my WinNT PIII 800Mhz machine with ActiveState 522 both of these are faster than ase's Bit Vector implementation. <p> <code> Carl1: @p=(1);for(2..10000){if(!$n[$_]){push@p,$_;for($k=$_*$_;$k<=10000;$n[$k]=1,$k+=$_){}}} Carl2: @p=(1,2);for($_=3;$_<=10000;$_+=2){if(!$n[$_]){push@p,$_;for($k=$_*$_;$k<=10000;$n[$k]=1,$k+=$_){}}} </code> One thing that I found interesting is that for n less than about 10,000, Carl1 is significantly faster than Carl2. The loop control overhead must be pretty significant. <p> Have fun,<br> Carl Forde 20633 20730