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 A178998 #22 May 19 2019 06:37:54
%S A178998 7,13,119923,146050183,4039362385345521139,
%T A178998 289247481259011497824466400997481269,
%U A178998 1765256712749403700417549596608786383,395766070055468241613007225643003404495980782673,2596786183076854435238229837938226284218037897451862682304077097493117
%N A178998 Primes of the form 4^k mod 3^k.
%F A178998 { A000040 } intersect { A064629 }.
%p A178998 select(isprime, [4&^n mod 3^n$n=1..200])[]; # _Alois P. Heinz_, May 18 2019
%t A178998 Select[Table[PowerMod[4, n, 3^n], {n, 100}], PrimeQ] (* _Alonso del Arte_, Jan 03 2011 *)
%o A178998 (PARI) terms(n) = my(i=0); for(k=0, oo, if(i>=n, break); my(x=lift(Mod(4, 3^k)^k)); if(ispseudoprime(x), print1(x, ", "); i++))
%o A178998 /* Print initial 7 terms as follows: */
%o A178998 terms(7) \\ _Felix Fröhlich_, May 18 2019
%Y A178998 Cf. A000040, A000079, A000244, A064629, A178985.
%K A178998 nonn
%O A178998 1,1
%A A178998 _Juri-Stepan Gerasimov_, Jan 03 2011