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 A281734 #15 May 25 2024 17:57:59 %S A281734 0,1,3,4,7,9,16,18,21,33,34,45,49,57,567,595,685,867,1867,4204,5311, %T A281734 11493,13923,19116,30471,32038,34551,99408,113631,134364,195399 %N A281734 Numbers k such that (2*10^k + 529)/9 is prime. %C A281734 For k > 1, numbers k such that k-2 occurrences of the digit 2 followed by the digits 81 is prime (see Example section). %C A281734 a(32) > 2*10^5. %H A281734 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A281734 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 2w81</a>. %e A281734 3 is in this sequence because (2*10^3 + 529)/9 = 281 is prime. %e A281734 Initial terms and associated primes: %e A281734 a(1) = 0, 59; %e A281734 a(2) = 1, 61; %e A281734 a(3) = 3, 281; %e A281734 a(4) = 4, 2281; %e A281734 a(5) = 7, 2222281; etc. %t A281734 Select[Range[0, 100000], PrimeQ[(2*10^# + 529)/9] &] %Y A281734 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A281734 nonn,more,hard %O A281734 1,3 %A A281734 _Robert Price_, Jan 28 2017 %E A281734 a(29)-a(31) from _Robert Price_, Jan 02 2018