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 A275802 #14 May 26 2024 14:59:22 %S A275802 1,2,4,5,7,10,16,19,28,37,41,44,53,311,490,1252,4360,4732,5575,6833, %T A275802 8878,11171,11396,13079,14903,76615 %N A275802 Numbers k such that (76*10^k + 167)/9 is prime. %C A275802 For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 4 followed by the digits 63 is prime (see Example section). %C A275802 a(27) > 10^5. %H A275802 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A275802 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 84w63</a>. %e A275802 4 is in this sequence because (76*10^4+167)/9 = 84463 is prime. %e A275802 Initial terms and associated primes: %e A275802 a(1) = 1, 103; %e A275802 a(2) = 2, 863; %e A275802 a(3) = 4, 84463; %e A275802 a(4) = 5, 844463; %e A275802 a(5) = 7, 84444463, etc. %t A275802 Select[Range[0, 100000], PrimeQ[(76*10^#+167)/9] &] %o A275802 (PARI) is(n)=ispseudoprime((76*10^n+167)/9) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A275802 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A275802 nonn,more %O A275802 1,2 %A A275802 _Robert Price_, Aug 09 2016