Elegant code & Efficient code

Elegant code & Efficient code, are they inversly proportional?

oh wait, the code in >>8 is even more broken than i thought...

the code in >>5 returns (2,2,5) for 20.
2 and 5 are both prime.
2*2*5==20

the code in >>8 returns (2,4,5,10,20) for 20.
4, 10, and 20 are not prime.
2*4*5*10*20!=20
MASSIVE FAIL.