
COMMENTS

Start of run of 3 consecutive numbers in A033948.
The next term is 3^541  2, which is too large to be included here. No more terms below 3^100000, or approximately 1.33*10^47712.
There is a multiple of 4 in every four consecutive positive integers and it clearly has no primitive roots if it is larger than 4. Again, there is a multiple of 3 in every three consecutive positive integers, so it must be a power of 3 or two times a power of 3, and the other two numbers must be odd prime powers or two times odd prime powers.
According to Pillai's conjecture, there're only finitely many solutions to 3^a  p^b = 2, 3^a  2*p^b = 1, p^a  2*3^b = 1 with a,b >= 2, p odd primes (no solution other than 3^3  5^2 = 2, 3^5  2*11^2 = 1 below 3^100000). So beyond (25, 26, 27) and (241, 242, 243), it's very likely that all three consecutive numbers with primitive roots are of the form (3^i, 3^i + 1, 3^i + 2), (3^j  2, 3^j  1, 3^j), (2*3^k  1, 2*3^k, 2*3^k + 1) such that (3^i + 1)/2, 3^i + 2, 3^j  2, (3^j  1)/2, 2*3^k  1, 2*3^k + 1 are primes, which only produces one more solution (3^541  2, 3^541  1, 3^541) below 3^1000000.


EXAMPLE

81, 82, 83 all have primitive roots (in fact, their least common primitive root is 47), so 81 is a term.
Note that A014224 and A028491 have a term 541 in common, so 3^541  2, 3^541  1 and 3^541 all have primitive roots, so 3^541  2 is a term.
