Longest Collatz sequence

Question

Which starting number, under 10,000, produces the longest chain?

NOTE: Once the chain starts the terms are allowed to go above 10,000.

What do you think? worthy?

https://code.sololearn.com/cvJ37F0fa2Io/?ref=app

Answer 1

Under 2,500,000 it's 2,298,025 with 559 iterations.
https://code.sololearn.com/cTrFw7PNJuaB/?ref=app