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 A104089 #8 Oct 28 2024 17:08:56 %S A104089 3,13,61,251,1021,4093,16381,65521,262139,1048573,4194301,16777213, %T A104089 67108859,268435399,1073741789,4294967291,17179869143,68719476731, %U A104089 274877906899,1099511627689,4398046511093,17592186044399,70368744177643 %N A104089 Largest prime <= 4^n. %F A104089 a(n) = A007917(A000302(n)). - _Paolo Xausa_, Oct 28 2024 %t A104089 NextPrime[4^Range[30], -1] (* _Paolo Xausa_, Oct 28 2024 *) %o A104089 (PARI) g(n,b) = for(x=0,n,print1(precprime(b^x)",")) %Y A104089 Cf. A014234, A104082, A104088, A104090-A104094, A003618, A104096. %Y A104089 Cf. A000040, A000302, A007917. %K A104089 easy,nonn %O A104089 1,1 %A A104089 _Cino Hilliard_, Mar 03 2005