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 A064629 #26 Sep 08 2022 08:45:04
%S A064629 0,1,7,10,13,52,451,1075,6487,6265,44743,119923,302545,147298,589192,
%T A064629 11922706,33341917,4227505,146050183,584200732,1174541461,4698165844,
%U A064629 18792663376,43789593895,175158375580,700633502320,1955245399837,2737249942690,18574597255747
%N A064629 a(n) = 4^n mod 3^n.
%C A064629 (a(n+1) - 4*a(n))/3^n is always one of -3, -2, -1, 0, 1, 2. - _Robert Israel_, Dec 01 2016
%H A064629 Harry J. Smith and Seiichi Manyama, <a href="/A064629/b064629.txt">Table of n, a(n) for n = 0..2096</a> (first 201 terms from Harry J. Smith)
%p A064629 A064629:=n->4^n mod 3^n: seq(A064629(n), n=0..40); # _Wesley Ivan Hurt_, Dec 01 2016
%t A064629 Table[PowerMod[4,n,3^n],{n,0,30}] (* _Harvey P. Dale_, Aug 26 2012 *)
%o A064629 (PARI) { f=t=1; for (n=0, 200, write("b064629.txt", n, " ", f%t); f*=4; t*=3 ) } \\ _Harry J. Smith_, Sep 20 2009
%o A064629 (Sage) [power_mod(4,n,3^n)for n in range(0,27)] # _Zerinvary Lajos_, Nov 28 2009
%o A064629 (Magma) [4^n mod 3^n: n in [0..40]]; // _Wesley Ivan Hurt_, Dec 01 2016
%Y A064629 Cf. A002379, A060692, A064628.
%Y A064629 Cf. k^n mod (k-1)^n: A002380 (k=3), this sequence (k=4), A138589 (k=5), A138649 (k=6), A139786 (k=7), A138973 (k=8), A139733 (k=9).
%K A064629 nonn,easy
%O A064629 0,3
%A A064629 _Labos Elemer_, Oct 01 2001
%E A064629 a(26) from _Harry J. Smith_, Sep 20 2009