# [racket] Why is this slow?

Jens Axel Søgaard <jensaxel at soegaard.net> writes:
>* I better take the blame for the number-theory collection :-)
*Ah, sorry for the miss attribution.
>* In the number-theory module I used remainders modulo 60=2*2*3*5.
*>* The trick is that there are exactly 16 numbers modulo 60, that
*>* stems from non-primes. One can therefore represent the block of 60
*>* remainders in only 2 bytes. See the gory details in:
*>*
*>* https://github.com/plt/racket/blob/master/collects/math/private/number-theory/small-primes.rkt
*
I looked at that for quite a while (it is wonderful that so much of racket is
written in racket) but never quite "got it" I think that method is called the
Atkin Sieve? As I said it is still over my head, but it seems like their would
be a straight forward way to provide your sieve from that module?
Thanks,
Jordan