The CPython interpreter in Python 3.14 can use a feature in C code that uses tail calls between functions. When compiled with a C compiler that supports these features, CPython runs slightly faster.

Try running this program with Python 3.12 or Python 3.13 (the GIL version). On my AMD Ryzen 3600 six-core machine, it completes in about two seconds. With Python 3.13t, it completes in about 0.6 ...