In C the random tests are merely 100 (necessarily repetitive) selections from 15 of the first 16 precomputed answers (omitting num_primorial(0)), instead of running a reference implementation on random inputs. I understand the range of inputs is narrowed by the forumla and native data types, but it seems silly to call that random anyway.

P.S. precomputation is valid strategy and indeed the best thing for some limited inputs.

P.P.S. multiplying the 17th prime overflows unsigned long long anyway.

I just did it in c++, and if you look at the most voted answers there, you'll get sad u.u

In which language there are no random test?

It should have some hidden test cases on Attempt to avoid some persons to write a map with the test cases as answer

Best solution, its clever and best practice at the same time

Finally a O(n) solution in the top solutions of this kata :)