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 A168430 #30 Feb 08 2025 13:57:45
%S A168430 1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,
%T A168430 10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,
%U A168430 9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10,1,4,3,12,9,10
%N A168430 a(n) = 4^n mod 13.
%H A168430 Vincenzo Librandi, <a href="/A168430/b168430.txt">Table of n, a(n) for n = 0..1000</a>
%H A168430 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, -1, 1).
%F A168430 From _R. J. Mathar_, Apr 13 2010: (Start)
%F A168430 a(n) = a(n-1) - a(n-3) + a(n-4).
%F A168430 G.f.: (1 + 3*x - x^2 + 10*x^3)/ ((1-x) * (1+x) * (x^2-x+1)). (End)
%F A168430 From _Wesley Ivan Hurt_, Sep 08 2022: (Start)
%F A168430 a(n) = (39-13*(-1)^n-20*cos(n*Pi/3)-12*sqrt(3)*sin(n*Pi/3))/6.
%F A168430 a(n) = a(n-6) for n >= 6. (End)
%t A168430 PowerMod[4,Range[0,100],13] (* or *) PadRight[{},100,{1,4,3,12,9,10}] (* _Harvey P. Dale_, Mar 15 2015 *)
%o A168430 (Sage) [power_mod(4, n, 13)for n in range(0, 90)]
%o A168430 (PARI) a(n)=lift(Mod(4,13)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%o A168430 (Magma) [Modexp(4, n, 13): n in [0..100]]; // _Vincenzo Librandi_, Jul 23 2016
%o A168430 (Magma) &cat[[1,4, 3,12,9,10]^^20]; // _Vincenzo Librandi_, Jul 23 2016
%K A168430 nonn,easy
%O A168430 0,2
%A A168430 _Zerinvary Lajos_, Nov 25 2009