Programming puzzle: Longest list of regular numbers?

[e_emil]

Nice code Han! As pier4r says, our sequences begin with two.

I looked at examples from oeis and I attacked Challenge 2 with the first Mathematica code, just changing the range to 604661760 since we already know it's the 1429th number (or 1430th, counting from one). Using the built-in EulerPhi[] function in a loop isn't a recipe for an efficient calculation, so the execution time won't surprise you: 6383 seconds (1 hour 46 minutes) on a fairly modern dell laptop.

Han's hp48 calculation was over 30 times faster than this!