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 A139739 #11 Sep 08 2022 08:45:33
%S A139739 0,1,19,271,3439,40951,468559,434062,13906558,225159022,3026431198,
%T A139739 5856821173,152711390557,2374402515013,8492830180156,176435471621404,
%U A139739 734899055740795,16614091501667155,99432188218005274,544037976289055377,2738676327544569592
%N A139739 a(n) = 10^n mod 9^n.
%H A139739 Vincenzo Librandi, <a href="/A139739/b139739.txt">Table of n, a(n) for n = 0..300</a>
%t A139739 Table[PowerMod[10,n,9^n],{n,0,20}] (* _Harvey P. Dale_, Dec 15 2013 *)
%o A139739 (Magma) [10^n mod 9^n: n in [0..20]]; // _Vincenzo Librandi_, Jun 02 2011
%K A139739 nonn
%O A139739 0,3
%A A139739 _N. J. A. Sloane_, May 20 2008