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 A290241 #20 Jun 17 2025 02:59:38
%S A290241 19,73,2179,6553,4782961,3486784393,31381059601,
%T A290241 381520424476945831628649898801,
%U A290241 2088595827392656793085408064780643444068898148936888424953199350259
%N A290241 Primes of the form 3^k - 8.
%H A290241 Robert Price, <a href="/A290241/b290241.txt">Table of n, a(n) for n = 1..11</a>
%H A290241 F. Firoozbakht and M. F. Hasler, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL13/Hasler/hasler2.html">Variations on Euclid's formula for Perfect Numbers</a>, JIS 13 (2010) #10.3.1.
%H A290241 Henri and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop">PRP Records</a>
%H A290241 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%F A290241 a(n) = 3^A217135(n) - 8. - _Elmo R. Oliveira_, Nov 09 2023
%t A290241 Select[Table[3^k - 8, {k, 2, 100}], PrimeQ[#] &]
%o A290241 (PARI) lista(nn) = for(n=3, nn, if(isprime(p=3^n-8), print1(p", "))); \\ _Altug Alkan_, Jul 25 2017
%Y A290241 Cf. A000040, A217135 (corresponding k's).
%K A290241 nonn
%O A290241 1,1
%A A290241 _Robert Price_, Jul 24 2017