I asked my prolog what the value of N was and it told me:
Welcome to SWI-Prolog (Multi-threaded, Version 5.6.14)
Copyright (c) 1990-2006 University of Amsterdam.
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.
For help, use ?- help(Topic). or ?- apropos(Word).
... 1,000,000 ............ 10,000,000 years later
% >> 42 << (last release gives the question)