cp's OEIS Frontend

All terms correspond to verified primes, that is, not merely probable primes.

a(14) > 2*10^5.

All terms are odd, since if k were even, N = 2^4 * 3^k would be a perfect square and N - 1 could be factored as the difference of squares, hence not prime.

a(21) > 10^5. - Michael S. Branicky, Aug 15 2025

a(28) > 10^5.

Conjecture: This sequence intersects with A387201 at k = 4 to form twin primes with center N = 2^5 * 3^4 = 2592 = A027856(10). Any such intersection has to be at an even k because if k is odd, either N-1 or N+1 has to be divisible by 5. A covering system can be constructed that eliminates all other intersections except where k = 4(mod 60), and for k > 4 with k = 4(mod 60), the search up to 10^5 makes the probability of another intersection in this residue class vanishingly small.