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 A125856 #7 Oct 19 2017 03:15:04
%S A125856 4,2,83270,5241160,57171410,359829200
%N A125856 a(n) = least number k such that k^(2^n)+1, k^(2^n)+3, k^(2^n)+7 and k^(2^n)+9 are all prime.
%C A125856 In 1958, Schinzel showed that for each n>0, there are infinitely many primes among the numbers k^(2^n)+{1,3,7, or 9}.
%D A125856 Sierpinski, W. Elementary theory of numbers. Warszawa 1964 Monografie Matematyczne Vol. 42.
%o A125856 (PARI) a(n) = {k = 1; while(!isprime(k^(2^n)+1) || !isprime(k^(2^n)+3) || !isprime(k^(2^n)+7) || !isprime(k^(2^n)+9), k++); k;} \\ _Michel Marcus_, Nov 03 2013
%Y A125856 Cf. A125855, A057015, A125779, A125780.
%K A125856 nonn
%O A125856 0,1
%A A125856 _Artur Jasinski_, Dec 12 2006
%E A125856 Edited by _Don Reble_, Dec 16 2006
%E A125856 One more term from _Farideh Firoozbakht_, Jan 01 2007