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 A273403 #13 Jul 30 2023 01:38:18 %S A273403 2,31,103,617,10253,10691,35353,129587,556441 %N A273403 Numbers k such that (10^k - 7^k)/3 is prime. %C A273403 All terms are prime. %C A273403 The corresponding primes: 17, 3333280741539321718064461652419, ... %H A273403 Jon Grantham and Andrew Granville, <a href="https://arxiv.org/abs/2307.07894">Fibonacci primes, primes of the form 2^n-k and beyond</a>, arXiv:2307.07894 [math.NT], 2023. %t A273403 Select[Range[1, 10000], PrimeQ[(10^# - 7^#)/3] &] %o A273403 (PARI) for(n=1, 10000, if(isprime((10^n - 7^n)/3), print1(n, ", "))) %Y A273403 Cf. A004023, A128026, A062576. %K A273403 nonn,more,hard %O A273403 1,1 %A A273403 _Tim Johannes Ohrtmann_, May 21 2016 %E A273403 a(7)-a(9) from _Jon Grantham_, Jul 29 2023