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 A098681 #13 Mar 10 2020 19:17:16
%S A098681 3,23,251,3121,46649,823541,16777213,387420479,9999999967,
%T A098681 285311670569,8916100448237,302875106592241,11112006825557999,
%U A098681 437893890380859323,18446744073709551557,827240261886336764159,39346408075296537575359
%N A098681 Largest prime smaller than n^n.
%H A098681 Hugo Pfoertner, <a href="/A098681/b098681.txt">Table of n, a(n) for n = 2..386</a>
%t A098681 PrimePrev[n_]:=Module[{k},k=n-1;While[ !PrimeQ[k],k-- ];k];f[n_]:=n^n;lst={};Do[AppendTo[lst,PrimePrev[f[n]]],{n,30}];lst (* _Vladimir Joseph Stephan Orlovsky_, Feb 25 2010 *)
%t A098681 Table[NextPrime[n^n,-1],{n,2,20}] (* _Harvey P. Dale_, Dec 02 2017 *)
%Y A098681 Cf. A000312, A074967, A098682, A161503, A333184.
%K A098681 easy,nonn
%O A098681 2,1
%A A098681 _Olaf Voß_, Oct 27 2004