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 A062594 #17 Jul 04 2021 07:52:49 %S A062594 3,5,19,31,257,773 %N A062594 Numbers k such that 28^k - 27^k is prime. %C A062594 Terms > 1000 are often only strong pseudoprimes. %C A062594 a(7) > 10^5. - _Robert Price_, Sep 04 2012 %o A062594 (PARI) is(n)=ispseudoprime(28^n-27^n) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A062594 Cf. A000043, A057468, A059801, A059802, A062572-A062666. %K A062594 nonn,hard %O A062594 1,1 %A A062594 _Mike Oakes_, May 18 2001, May 19 2001