assert(CW6a.collatz_max(10) == (20, 9))

assert(CW6a.collatz_max(100) == (119, 97))

assert(CW6a.collatz_max(1000) == (179, 871))

assert(CW6a.collatz_max(10000) == (262, 6171))

assert(CW6a.collatz_max(100000) == (351, 77031))

assert(CW6a.collatz_max(1000000) == (525, 837799))