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 A165508 Numbers k such that 10^k + 111 is prime. 1
 2, 4, 184, 460, 784, 3248, 5194, 92386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Terms must be congruent to 2 or 4 mod 6. Other than the first term, which produces 10^2 + 111 = 211, these terms produce primes whose decimal representation is 1 111 concatenated. These are only known to be highly probable primes for 184 and beyond. No more terms up to 15000. a(8) > 55000. - Tyler NeSmith, Jul 10 2021 The corresponding primes have digit sum 4 (A062339). - Jeppe Stig Nielsen, Feb 10 2023 a(9) > 10^5. - Jeppe Stig Nielsen, Feb 11 2023 LINKS Table of n, a(n) for n=1..8. EXAMPLE As 10111 = 10^4 + 111 is a prime, 4 is a term. MATHEMATICA Select[Range[5200], PrimeQ[10^# + 111] &] (* G. C. Greubel, Oct 21 2018 *) PROG (PARI) is(k)=ispseudoprime(10^k+111) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A096912, A157711, A062339, A020449, A036929, A161786. Sequence in context: A012369 A009609 A012367 * A018633 A307556 A018637 Adjacent sequences: A165505 A165506 A165507 * A165509 A165510 A165511 KEYWORD nonn,more AUTHOR Rick L. Shepherd, Sep 21 2009 EXTENSIONS a(8) from Jeppe Stig Nielsen, Feb 10 2023 STATUS approved

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Last modified July 13 17:55 EDT 2024. Contains 374285 sequences. (Running on oeis4.)