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 A181655 #18 Apr 06 2019 08:45:23
%S A181655 1,2,4,7,14,22,44,67,134,202,404,607,1214,1822,3644,5467,10934,16402,
%T A181655 32804,49207,98414,147622,295244,442867,885734,1328602,2657204,
%U A181655 3985807,7971614,11957422,23914844,35872267,71744534,107616802,215233604
%N A181655 Expansion of (1+2x-x^3+x^4)/(1-4x^2+3x^4).
%C A181655 Row sums of A181654.
%H A181655 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-3).
%F A181655 G.f.: (1+2*x-x^3+x^4)/((1-x^2)*(1-3*x^2)).
%F A181655 a(n) = 5*A038754(n+1)/6 - A040001(n)/2. - _R. J. Mathar_, May 14 2016
%F A181655 a(2n-1) = A060816(n-1), a(2n) = A198643(n-1); n >= 1. a(n+1) = 2*a(n) if n is odd. - _M. F. Hasler_, Apr 06 2019
%t A181655 CoefficientList[Series[(1+2x-x^3+x^4)/(1-4x^2+3x^4),{x,0,40}],x] (* or *) Join[{1},LinearRecurrence[{0,4,0,-3},{2,4,7,14},40]] (* _Harvey P. Dale_, Jan 11 2012 *)
%o A181655 (PARI) A181655(n)=if(bitand(n,1), 3^(n\2)*5\2, n, 3^(n\2-1)*5-1, 1) \\ _M. F. Hasler_, Apr 06 2019
%Y A181655 Cf. A060816, A198643 (bisections).
%K A181655 easy,nonn
%O A181655 0,2
%A A181655 _Paul Barry_, Nov 03 2010