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 A276492 #15 Jun 02 2024 14:03:38 %S A276492 1,3,7,9,10,19,21,22,43,46,58,87,216,549,604,1147,1858,2952,3684,4057, %T A276492 4246,4354,8212,8289,9013,16968,19107,57754,61348,88254 %N A276492 Numbers k such that 5*10^k + 59 is prime. %C A276492 For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 0 followed by the digits 59 is prime (see Example section). %C A276492 a(31) > 2*10^5. %H A276492 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A276492 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 50w59</a>. %e A276492 3 is in this sequence because 5*10^3 + 59 = 5059 is prime. %e A276492 Initial terms and associated primes: %e A276492 a(1) = 1, 109; %e A276492 a(2) = 3, 5059; %e A276492 a(3) = 7, 50000059; %e A276492 a(4) = 9, 5000000059; %e A276492 a(5) = 10, 50000000059, etc. %t A276492 Select[Range[0, 100000], PrimeQ[5*10^# + 59] &] %o A276492 (PARI) is(n)=ispseudoprime(5*10^n + 59) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A276492 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A276492 nonn,more %O A276492 1,2 %A A276492 _Robert Price_, Sep 05 2016