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 A289051 #8 May 19 2024 21:54:47 %S A289051 1,2,3,7,16,53,95,105,125,163,358,423,562,1774,3459,13957,17962,51179, %T A289051 65963,72808 %N A289051 Numbers k such that 13*10^k + 1 is prime. %C A289051 For k > 0, numbers k such that the digits 13 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section). %C A289051 a(21) > 10^5. %H A289051 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A289051 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 130w1</a>. %e A289051 2 is in this sequence because 13*10^3 + 1 = 1301 is prime. %e A289051 Initial terms and associated primes: %e A289051 a(1) = 1, 131; %e A289051 a(2) = 2, 1301; %e A289051 a(3) = 3, 13001; %e A289051 a(4) = 7, 130000001; %e A289051 a(5) = 16, 130000000000000001; etc. %t A289051 Select[Range[0, 100000], PrimeQ[13*10^# + 1] &] %Y A289051 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A289051 nonn,more,hard %O A289051 1,2 %A A289051 _Robert Price_, Jun 22 2017