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 A285377 #14 Jun 08 2024 15:41:31 %S A285377 3,5,6,9,11,53,105,125,137,228,789,1259,1661,1697,1785,3737,6054,7614, %T A285377 11819,27366,28320,48678,69321,76067,97085 %N A285377 Numbers k such that (41*10^k + 373)/9 is prime. %C A285377 For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 5 followed by the digits 97 is prime (see Example section). %C A285377 a(26) > 2*10^5. %H A285377 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A285377 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 45w97</a>. %e A285377 5 is in this sequence because (41*10^5 + 373)/9 = 455597 is prime. %e A285377 Initial terms and associated primes: %e A285377 a(1) = 3, 4597; %e A285377 a(2) = 5, 455597; %e A285377 a(3) = 6, 4555597; %e A285377 a(4) = 9, 4555555597; %e A285377 a(5) = 11, 455555555597; etc. %t A285377 Select[Range[0, 100000], PrimeQ[(41*10^# + 373)/9] &] %Y A285377 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A285377 nonn,more,hard %O A285377 1,1 %A A285377 _Robert Price_, Apr 17 2017