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 A131712 #37 Sep 09 2024 14:56:13
%S A131712 1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,
%T A131712 7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,
%U A131712 1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1,3,7,9,1
%N A131712 Period 4: repeat [1, 3, 7, 9].
%C A131712 Decimal expansion of 1379/9999. - _Klaus Brockhaus_, May 21 2010
%H A131712 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,1).
%F A131712 G.f.: (1+3*x+7*x^2+9*x^3)/((1-x)*(x+1)*(1+x^2)). - _R. J. Mathar_, Nov 14 2007
%F A131712 From _Wesley Ivan Hurt_, Jul 09 2016: (Start)
%F A131712 a(n) = a(n-4) for n>3.
%F A131712 a(n) = 5 - 3*cos(n*Pi/2) - cos(n*Pi) - 3*sin(n*Pi/2) - I*sin(n*Pi). (End)
%p A131712 seq(op([1, 3, 7, 9]), n=0..40); # _Wesley Ivan Hurt_, Jul 09 2016
%t A131712 PadRight[{}, 100, {1, 3, 7, 9}] (* _Wesley Ivan Hurt_, Jul 09 2016 *)
%o A131712 (PARI) a(n)=1+2*(n%4)+2*(n%4\2) \\ _Jaume Oliver Lafont_, Aug 28 2009
%o A131712 (Magma) &cat[[1, 3, 7, 9]: k in [1..30]]; // _Vincenzo Librandi_, Nov 23 2010
%Y A131712 Cf. A072845, A131707.
%Y A131712 Cf. A178148 (decimal expansion of (243+17*sqrt(285))/402). - _Klaus Brockhaus_, May 21 2010
%K A131712 nonn,easy
%O A131712 0,2
%A A131712 _Paul Curtz_, Sep 14 2007
%E A131712 More terms from _Klaus Brockhaus_, May 21 2010