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 A137445 #15 Apr 20 2019 08:45:17
%S A137445 3,2,-2,-8,-12,-8,8,32,48,32,-32,-128,-192,-128,128,512,768,512,-512,
%T A137445 -2048,-3072,-2048,2048,8192,12288,8192,-8192,-32768,-49152,-32768,
%U A137445 32768,131072,196608,131072,-131072,-524288,-786432,-524288,524288
%N A137445 a(n) = 2a(n-1)-2a(n-2), with a(0)=3 and a(1)=2.
%H A137445 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-2).
%F A137445 O.g.f.: (3-4x)/(1-2x+2x^2). a(n)=(-1)^(n+1)*A134142(n+1). - _R. J. Mathar_, May 01 2008
%F A137445 a(n) = (3/2 - I/2)*(1 - I)^n + (3/2 + I/2)*(1 + I)^n, n>=0. - _Taras Goy_, Apr 20 2019
%t A137445 LinearRecurrence[{2,-2},{3,2},40] (* _Harvey P. Dale_, May 03 2018 *)
%K A137445 sign
%O A137445 0,1
%A A137445 _Paul Curtz_, Apr 18 2008
%E A137445 More terms from _R. J. Mathar_, May 01 2008