User blog comment:Deedlit11/Bignum Bakeoff appetizer/@comment-5529393-20140916022609/@comment-5529393-20140916102155

Hmm, I may have been mistaken on my last  post. It looks like you are saying that b gets incremented to 2 before u gets called. And it does indeed look like i gets incremented before o*b <= n is checked, so it will reach 2 before the test fails. So yes, it does look like there is  a bug.