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 A078305 #14 Jul 23 2023 17:00:44
%S A078305 3,4,5,6,7,13,14,19,20,28,37,99,100,108,141,304,442,682,3641,4076
%N A078305 Numbers k such that A004154(k) - 1 is prime.
%C A078305 Some of the larger entries may only correspond to probable primes.
%t A078305 f[n_] := n!/10^Sum[ Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ f[n] - 1], Print[n]], {n, 1, 750}]
%Y A078305 Cf. A004154, A078154, A078203, A078190.
%K A078305 nonn,base,more
%O A078305 1,1
%A A078305 _Cino Hilliard_, Dec 23 2002
%E A078305 Extended by _Robert G. Wilson v_ and _Jason Earls_, Dec 24 2002
%E A078305 a(19)-a(20) from _Michael S. Branicky_, Jul 23 2023