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For k> > 1, numbers k such that the digit 1 followed by k-2 occurrences of the digit 6 followed by the digits 33 is prime (see Example section).
Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/primedifficultyprime_difficulty.txt">Search for 16w33.</</a>>.
Initial terms and primes associated primes:
4, 19, 29, 42, 48, 57, 70, 71, 72, 124, 189, 216, 1860, 4170, 6132, 9226, 9725, 9906, 9942, 15283, 19386, 181950, 219847, 234054
a(2325) > 23*10^5.
a(23)-a(24) from Robert Price, Oct 25 2023
Makoto Kamada, <a href="httphttps://stdkmd.comnet/nrr">Factorization of near-repdigit-related numbers</a>.
Makoto Kamada, <a href="httphttps://stdkmd.comnet/nrr/prime/primedifficulty.txt">Search for 16w33.</a>
OEIS Server: https://oeis.org/edit/global/2791