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 A135575 #10 Oct 19 2016 23:06:46
%S A135575 0,3,-5,9,-16,30,-63,129,-257,513,-1024,2046,-4095,8193,-16385,32769,
%T A135575 -65536,131070,-262143,524289,-1048577,2097153,-4194304,8388606,
%U A135575 -16777215,33554433,-67108865,134217729,-268435456,536870910,-1073741823,2147483649,-4294967297,8589934593
%N A135575 a(n) = A135574(n+1) - 2*A135574(n).
%H A135575 G. C. Greubel, <a href="/A135575/b135575.txt">Table of n, a(n) for n = 0..1000</a>
%H A135575 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (-2,-1,-2,-1,-2).
%F A135575 G.f.: x*(3*x^3+2*x^2+x+3)/((2*x+1)*(x^2+x+1)*(x^2-x+1)). - Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009
%F A135575 a(n) + 2*a(n-1) + a(n-2) + 2*a(n-3) + a(n-4) + 2*a(n-5) = 0. - _G. C. Greubel_, Oct 19 2016
%p A135575 A024495 := proc(n) option remember ; if n <=1 then 0 ; elif n = 2 then 1; elif n = 3 then 3 ; else A024495(n-1)-A024495(n-2)+2^(n-2) ; fi ; end: A135574 := proc(n) option remember ; A024495(2*floor(n/2)+1 - ( n mod 2)) ; end: A135575 := proc(n) A135574(n+1)-2*A135574(n) ; end: seq(A135575(n),n=0..80) ; # _R. J. Mathar_, Mar 31 2008
%t A135575 LinearRecurrence[{-2, -1, -2, -1, -2}, {0, 3, -5, 9, -16}, 25] (* _G. C. Greubel_, Oct 19 2016 *)
%o A135575 (PARI) a(n)=([0,1,0,0,0; 0,0,1,0,0; 0,0,0,1,0; 0,0,0,0,1; -2,-1,-2,-1,-2]^n*[0;3;-5;9;-16])[1,1] \\ _Charles R Greathouse IV_, Oct 19 2016
%K A135575 sign,easy
%O A135575 0,2
%A A135575 _Paul Curtz_, Feb 24 2008
%E A135575 More terms from _R. J. Mathar_, Mar 31 2008