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 A281732 #13 Jun 02 2024 14:04:49 %S A281732 3,5,9,20,26,77,101,120,308,543,869,876,1193,1199,1355,1923,3689,3788, %T A281732 4182,6539,19068,26922,38957,58872,61230,72759 %N A281732 Numbers k such that (8*10^k + 67)/3 is prime. %C A281732 For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 6 followed by the digits 89 is prime (see Example section). %C A281732 a(27) > 2*10^5. %H A281732 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A281732 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 26w89</a>. %e A281732 5 is in this sequence because (8*10^5 + 67)/3 = 2266689 7751 is prime. %e A281732 Initial terms and associated primes: %e A281732 a(1) = 3, 2689; %e A281732 a(2) = 5, 266689; %e A281732 a(3) = 9, 2666666689; %e A281732 a(4) = 20, 266666666666666666689; etc. %t A281732 Select[Range[0, 100000], PrimeQ[(8*10^# + 67)/3] &] %Y A281732 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A281732 nonn,more,hard %O A281732 1,1 %A A281732 _Robert Price_, Jan 28 2017