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 A273265 #15 May 02 2024 04:24:36 %S A273265 0,1,2,3,6,7,8,10,16,17,35,53,121,155,178,487,880,1153,2136,2790,2803, %T A273265 5775,5845,5971,7131,13213,13813,17153,31461,38735,93577,188457 %N A273265 Numbers k such that (16*10^k + 161)/3 is prime. %C A273265 For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 3 followed by the digits 87 is prime (see Example section). %C A273265 a(33) > 2*10^5. %H A273265 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A273265 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 53w87</a>. %e A273265 3 is in this sequence because (16*10^3 + 161)/3 = 5387 is prime. %e A273265 Initial terms and associated primes: %e A273265 a(1) = 0, 59; %e A273265 a(2) = 1, 107; %e A273265 a(3) = 2, 587; %e A273265 a(4) = 3, 5387; %e A273265 a(5) = 6, 5333387, etc. %t A273265 Select[Range[0, 100000], PrimeQ[(16*10^# + 161)/3] &] %o A273265 (PARI) is(n)=ispseudoprime((16*10^n + 161)/3) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A273265 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A273265 nonn,more %O A273265 1,3 %A A273265 _Robert Price_, May 18 2016 %E A273265 a(32) from _Robert Price_, Feb 27 2019