www.mikescher.com/www/statics/euler/Euler_Problem-058_explanation.md

It's obvious that the bottleneck of this program is the primality test. The numbers become here too big to create a sieve and "normal" prime testing takes too long. So we use the Miller-Rabin primality test that I implemented a while ago (thank mathblog.dk).
The rest is just enumerating all the diagonals until primes*10<all