This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A165508 #25 Nov 14 2024 23:49:30 %S A165508 2,4,184,460,784,3248,5194,92386,156428,228208 %N A165508 Numbers k such that 10^k + 111 is prime. %C A165508 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 <n-3 0's> 111 concatenated. These are only known to be highly probable primes for 184 and beyond. No more terms up to 15000. %C A165508 a(8) > 55000. - _Tyler NeSmith_, Jul 10 2021 %C A165508 The corresponding primes have digit sum 4 (A062339). - _Jeppe Stig Nielsen_, Feb 10 2023 %C A165508 a(9) > 10^5. - _Jeppe Stig Nielsen_, Feb 11 2023 %C A165508 a(11) > 6.6*10^5. - _Boyan Hu_, Nov 14 2024 %e A165508 As 10111 = 10^4 + 111 is a prime, 4 is a term. %t A165508 Select[Range[5200], PrimeQ[10^# + 111] &] (* _G. C. Greubel_, Oct 21 2018 *) %o A165508 (PARI) is(k)=ispseudoprime(10^k+111) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A165508 Cf. A096912, A157711, A062339, A020449, A036929, A161786. %K A165508 nonn,more %O A165508 1,1 %A A165508 _Rick L. Shepherd_, Sep 21 2009 %E A165508 a(8) from _Jeppe Stig Nielsen_, Feb 10 2023 %E A165508 a(9)-a(10) from _Boyan Hu_, Oct 23 2024