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 A131707 #25 Dec 12 2023 09:19:00
%S A131707 1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,7,3,
%T A131707 3,9,1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,
%U A131707 7,3,3,9,1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,7,3,3,9,1,1,3,7,7,1,9,9,7
%N A131707 Period 12: repeat 1, 1, 3, 7, 7, 1, 9, 9, 7, 3, 3, 9 .
%C A131707 Also the decimal expansion of 1023949/9000009. [_R. J. Mathar_, Feb 07 2009]
%H A131707 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,-1,1).
%F A131707 a(n) = A001333(n) mod 10. - _Paul Curtz_, Apr 08 2008
%F A131707 G.f.: (1+2x^2+4x^3-6x^5+9x^6)/((1-x)(1+x^2)(1-x^2+x^4)). a(n)=a(n-1)-a(n-6)+a(n-7). [_R. J. Mathar_, Feb 07 2009]
%F A131707 a(n) = 5-2*cos(Pi*n/6) -2*sin(Pi*n/6)/3 -10*sin(Pi*n/2)/3 -2*cos(5*Pi*n/6) -2*sin(5*Pi*n/6)/3. - _R. J. Mathar_, Oct 08 2011
%t A131707 PadRight[{},120,{1,1,3,7,7,1,9,9,7,3,3,9}] (* _Harvey P. Dale_, May 02 2012 *)
%Y A131707 Cf. A131711.
%K A131707 nonn,easy
%O A131707 0,3
%A A131707 _Paul Curtz_, Sep 14 2007
%E A131707 More terms from Tracy Poff (tracy.poff(AT)gmail.com), Dec 21 2008
%E A131707 Even more periods from _R. J. Mathar_, Feb 07 2009