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 A308553 #25 Nov 11 2024 14:14:13
%S A308553 0,4,8,524,972,3780,7704
%N A308553 Numbers k such that 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime.
%C A308553 Larger k values yield probable primes.
%C A308553 a(8) > 100000 (if it exists). - _Michael S. Branicky_, Nov 11 2024
%t A308553 ParallelTable[If[PrimeQ[5^(n+3) + 3^(n+2) + 2^(n+1) + 1], n, Nothing], {n, 0, 10^4}]
%Y A308553 Cf. A306573.
%K A308553 nonn,hard,more
%O A308553 1,2
%A A308553 _Mikk Heidemaa_, Jun 07 2019