same as big_int but will write and read the collatz sequence to/from a file "collatz_sequence.txt" to avoid system memory overflow when operating with extremly large integers. With this program I was able to compute 2^100000-1 in about 2 hours and 15 minutes. Size of "collatz_sequence.txt" was 35.2 GB. In this case I did not print the sequence in the terminal and only caluated the statistics.
Don't forget to adopt the constant with the path where to save the file collatz_sequence.txt.