Round 5

[bsvare]

I would give you Kudos Darren for a much simplier code (and faster running) then even I did, but yours is flawed. It doesn't handle numbers larger than an I32 which maxes out with a input of 23.

[Darren]

Oops, I didn't realize the I32 was rolling over. Ok fine, here it is with the math VI inlined so everything can operate on I64.

Spoiler

[GregSands]

How about bonus points for three different approaches?  I haven't benchmarked them against each other or other solutions.

Spoiler

First approach builds an array containing all necessary prime factors, the second keeps a running multiple, and the third is a different way of building the array.