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 A167291 #17 Jun 05 2016 23:49:59
%S A167291 2,2,0,0,8,8,-24,-24,104,104,-408,-408,1640,1640,-6552,-6552,26216,
%T A167291 26216,-104856,-104856,419432,419432,-1677720,-1677720,6710888,
%U A167291 6710888,-26843544,-26843544,107374184,107374184,-429496728,-429496728,1717986920,1717986920
%N A167291 a(n) = A137505(2n) + A137505(2n+1).
%C A167291 The formula for the singular sequence, i.e., just each unique term of the sequence (without duplication), is: a(n) = 1/10 (16-(-4)^n). - _Harvey P. Dale_, Jun 12 2013
%H A167291 G. C. Greubel, <a href="/A167291/b167291.txt">Table of n, a(n) for n = 0..1000</a>
%H A167291 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,-4,4)
%F A167291 a(2n) = a(2n+1) = 2*(-1)^n*A109499(n).
%F A167291 G.f. ( -2-6*x^2 ) / ( (x-1)*(4*x^2+1) ). - _R. J. Mathar_, Feb 06 2011
%F A167291 a(0)=2, a(1)=2, a(2)=0, a(n) = a(n-1)-4*a(n-2)+4*a(n-3). - _Harvey P. Dale_, Jun 12 2013
%t A167291 CoefficientList[Series[(-2-6x^2)/((x-1)(4x^2+1)),{x,0,50}],x] (* or *) LinearRecurrence[{1,-4,4},{2,2,0},50] (* _Harvey P. Dale_, Jun 12 2013 *)
%K A167291 easy,sign
%O A167291 0,1
%A A167291 _Paul Curtz_, Nov 01 2009