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For k > 1, numbers k such that the digit 7 followed by k - 2 occurrences of the digit 3 followed by the digits 27 is prime (see Example section).
Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/primedifficultyprime_difficulty.txt">Search for 73w27</a>.
Initial terms and primes associated primes:
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1, 2, 4, 6, 14, 15, 24, 48, 78, 112, 122, 334, 504, 872, 914, 1230, 1506, 2442, 4095, 5022, 10615, 11460, 18303, 33675, 47701, 55592, 84159, 146661, 269517, 287085
a(2931) > 23*10^5.
a(29)-a(30) from Robert Price, Oct 26 2023
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