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 A271884 #6 Apr 16 2016 11:43:05 %S A271884 1,2,4,6,10,12,30,42,54,166,264,886,1476,8412,9576,12426,24076 %N A271884 Numbers n such that 4^n-3^(n-1) is prime. %C A271884 a(18) > 10^5. %e A271884 4 is a member since 4^4 - 3^3 = 256 - 27 = 229 which is a prime number. %t A271884 Select[Range[0, 100000], PrimeQ[4^# - 3^(# - 1)] &] %o A271884 (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(4^n-3^(n-1)), print1(n, ", "))); \\ _Altug Alkan_, Apr 16 2016 %Y A271884 Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883. %K A271884 nonn,more %O A271884 1,2 %A A271884 _Robert Price_, Apr 16 2016