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 A141317 #10 Feb 10 2020 02:13:50
%S A141317 0,0,8,24,80,240,728,2184,6560,19680,59048,177144,531440,1594320,
%T A141317 4782968,14348904,43046720,129140160,387420488,1162261464,3486784400,
%U A141317 10460353200,31381059608,94143178824,282429536480,847288609440
%N A141317 a(n) = A000244(n) - A010684(n).
%H A141317 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,1,-3).
%F A141317 O.g.f.: 8*x^2/((1-3*x)*(1-x)*(1+x)). - _R. J. Mathar_, Aug 09 2008
%p A141317 A010684 := proc(n) 1+2*(n mod 2) ; end: A141317 := proc(n) 3^n-A010684(n) ; end: for n from 0 to 50 do printf("%d,",A141317(n)) ; od: # _R. J. Mathar_, Aug 09 2008
%t A141317 CoefficientList[Series[8x^2/((1-3x)(1-x)(1+x)),{x,0,30}],x] (* _Harvey P. Dale_, Sep 16 2019 *)
%K A141317 nonn
%O A141317 0,3
%A A141317 _Paul Curtz_, Aug 02 2008
%E A141317 Extended by _R. J. Mathar_, Aug 09 2008