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 A137797 #10 Jun 13 2015 00:52:35
%S A137797 0,4,4,8,-2,2,2,6,6,0,0,4,4,8,-2,2,2,6,6,0,0,4,4,8,-2,2,2,6,6,0,0,4,4,
%T A137797 8,-2,2,2,6,6,0,0,4,4,8,-2,2,2,6,6,0,0,4,4,8,-2,2,2,6,6,0,0,4,4,8,-2,
%U A137797 2,2,6,6,0,0,4,4,8,-2,2,2,6,6
%N A137797 a(n) = 2*( (n+1) mod 5 ) - 2*( (n+1) mod 2 ).
%C A137797 The sequence is periodic with period 10. - _Colin Barker_, Dec 16 2014
%H A137797 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (-1,0,0,0,1,1).
%F A137797 a(n) = -a(n-1)+a(n-5)+a(n-6) for n>5. - _Colin Barker_, Dec 16 2014
%F A137797 G.f.: -2*x*(3*x^3+6*x^2+4*x+2) / ((x-1)*(x+1)*(x^4+x^3+x^2+x+1)). - _Colin Barker_, Dec 16 2014
%e A137797 a(2) = 2*((2+1) mod 5) - 2*((2+1) mod 2) = 2*(3 mod 5) - 2*(3 mod 2) = 4.
%t A137797 LinearRecurrence[{-1,0,0,0,1,1},{0,4,4,8,-2,2},100] (* _Harvey P. Dale_, Jun 08 2015 *)
%o A137797 (PARI) concat(0, Vec(-2*x*(3*x^3+6*x^2+4*x+2)/((x-1)*(x+1)*(x^4+x^3+x^2+x+1)) + O(x^100))) \\ _Colin Barker_, Dec 16 2014
%Y A137797 Suggested by A010700. Used in A137798.
%K A137797 easy,sign
%O A137797 0,2
%A A137797 _William A. Tedeschi_, Feb 10 2008