Yeah, the article says they investigated in base 3 first. In that base, it can by 0, 1, or 2 mod 3 (for the final digit). Primes clearly aren't 0 mod 3, so al

Yeah, the article says they investigated in base 3 first. In that base, it can by 0, 1, or 2 mod 3 (for the final digit). Primes clearly aren't 0 mod 3, so all (not 3) primes end in 1 or 2. They found that primes "liked" to alternate between them.