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 A143252 #4 Jun 13 2017 12:57:38 %S A143252 0,1,819,1449,1677,13319 %N A143252 Numbers n such that 2*41^n + 1 is prime. %C A143252 Primes found and proved by PrimeForm. No more terms up to 30000. %o A143252 (PARI) is(n)=ispseudoprime(2*41^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A143252 Cf. A141802. %K A143252 hard,nonn %O A143252 1,3 %A A143252 _Rick L. Shepherd_, Aug 02 2008