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 A070421 #45 Dec 14 2023 05:06:34 %S A070421 1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7, %T A070421 11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1, %U A070421 7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11,1,7,11 %N A070421 a(n) = 7^n mod 38. %C A070421 Period 3: repeat [1, 7, 11]. %C A070421 Equivalently 7^n mod 19. - _Zerinvary Lajos_, Nov 27 2009 %H A070421 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1). %F A070421 From _R. J. Mathar_, Apr 20 2010: (Start) %F A070421 a(n) = a(n-3) for n>2. %F A070421 G.f.: ( 1+7*x+11*x^2 ) / ( (1-x)*(1+x+x^2) ). (End) %F A070421 a(n) = (19 - 16*cos(2*n*Pi/3) - 4*sqrt(3)*sin(2*n*Pi/3))/3. - _Wesley Ivan Hurt_, Jun 29 2016 %p A070421 seq(op([1, 7, 11]), n=0..50); # _Wesley Ivan Hurt_, Jun 29 2016 %t A070421 PowerMod[7, Range[0, 50], 38] (* _G. C. Greubel_, Mar 21 2016 *) %o A070421 (Sage) [power_mod(7,n,19) for n in range(0,90)] # or: %o A070421 [power_mod(7,n,38) for n in range(0,90)] # _Zerinvary Lajos_, Nov 27 2009 %o A070421 (PARI) a(n)=lift(Mod(7,19)^n) \\ _Charles R Greathouse IV_, Mar 22 2016 %o A070421 (Magma) [Modexp(7, n, 19): n in [0..100]]; // _Bruno Berselli_, Mar 22 2016 %K A070421 nonn,easy %O A070421 0,2 %A A070421 _N. J. A. Sloane_, May 12 2002