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 A181285 #12 Aug 02 2021 12:25:55
%S A181285 3121,78121,30517578121,710542735760100185871124267578121,
%T A181285 413590306276513837435704346034981426782906055450439453121
%N A181285 Primes of the form 5^k - 4.
%e A181285 3121 = 5^5 - 4 is prime and therefore is in the sequence.
%p A181285 n:=1000: S:={}: for i from 1 to n do if type(5^i-4,prime)=true then S:=S union {5^i-4} end if od; S;
%t A181285 Select[5^Range[90]-4,PrimeQ] (* _Harvey P. Dale_, Aug 23 2013 *)
%Y A181285 Cf. A059613, A135535, A228028.
%K A181285 nonn
%O A181285 1,1
%A A181285 _Jonathan D. B. Hodgson_, Oct 12 2010