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 A132358 #10 Jul 01 2020 19:43:28
%S A132358 2,3,13,251,65521,4294967291,18446744073709551557,
%T A132358 340282366920938463463374607431768211297,
%U A132358 115792089237316195423570985008687907853269984665640564039457584007913129639747
%N A132358 a(n) = greatest prime <= 2^(2^n).
%t A132358 a={}; For[n=0, n<10, n++, b=2^(2^n); While[ !PrimeQ[b], b=b-1]; AppendTo[a, b]]; a (* _Stefan Steinerberger_, Nov 12 2007 *)
%t A132358 If[PrimeQ[#],#,NextPrime[#,-1]]&/@(2^(2^Range[0,10])) (* _Harvey P. Dale_, Jul 01 2020 *)
%Y A132358 Cf. A132198.
%K A132358 nonn
%O A132358 0,1
%A A132358 _Leroy Quet_, Nov 08 2007
%E A132358 More terms from _Stefan Steinerberger_, Nov 12 2007