Thanks for catching that.  I just noticed the bug in my code, which is:  although I'm caching prime numbers, I'm not testing all of them as potential factors.

I'll go update the code now, but you're right; there needs to be a check for division by 2.

s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

In reply to Re^3: ulam's spiral too slow by liverpole
in thread ulam's spiral too slow by orange

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