Something special about 399 (and 2015) - Numberphile

It is the lowest Lucas-Carmichael Number... Featuring Ed Copeland. More about Ed’s real work: With thanks to these Patreon supporters: Herschal Sanders (from Susan) Today I Found Out Lê OK Merli Alex Bozzi Thomas J Petersen Spiked Math Filipe Junqueira Bill Shillito plusunim Micky Baeza Tracy Parry Andrzej ’Yester’ Fiedukowicz Stan Ciprian Rich Pantano (from Jill) Joshua Wilson & Andrew Touchet Kelly N Cooper Stimson Support us on Patreon: