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 A273524 #6 Jun 13 2017 14:43:28 %S A273524 2,3,5,6,7,11,17,18,54,509,529,2526,3042,3421,4485,13127,17602,23825, %T A273524 27381 %N A273524 Numbers n such that 7^n-6^(n-1) is prime. %C A273524 a(20) > 10^5. %t A273524 Select[Range[0, 100000], PrimeQ[7^# - 6^(# - 1)] &] %o A273524 (PARI) is(n)=ispseudoprime(7^n-6^(n-1)) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A273524 Cf. A093713, A093765. %K A273524 nonn,more %O A273524 1,1 %A A273524 _Robert Price_, May 23 2016