https://www.codingame.com/playgrounds/17176/recueil-dexercices-pour-apprendre-python-au-lycee/lalgorithme-deuclide
https://workshop.numworks.com/python/remy-cobena/euclide_etendu https://irem.univ-reunion.fr/spip.php?article715
https://rguejdad.com/articles/theoreme-lame-fibonacci-pgcd-grand-oral