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 A156561 #7 Jun 06 2016 14:41:49
%S A156561 0,0,0,1,3,9,25,67,177,464,1216,3184,8336,21824,57136,149585,391619,
%T A156561 1025273,2684201,7027331,18397793,48166048,126100352,330135008,
%U A156561 864304672,2262779008,5924032352,15509318049,40603921795,106302447337,278303420217
%N A156561 Floor(Fibonacci(2n+1)/9).
%H A156561 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (4, -4, 1, 0, 0, -1, 4, -4, 1).
%F A156561 a(n) = ( A000045(2n+1)-A154811(n) )/9 = floor(A122367(n)/9) = floor(A001519(n+1)/9) = floor( |A099496(n)|/9).
%F A156561 a(n)=3a(n-1)-a(n-2)+|A112690(n+10)|, i.e., a(n)-3a(n-1)+a(n-2) is a sequence of period 12 containing 0's and 1's. - _R. J. Mathar_, Feb 23 2009
%F A156561 G.f.: (1-x+x^2)/((1-x)(1+x^2)(1-3x+x^2)(1-x^2+x^4)). - _R. J. Mathar_, Feb 23 2009
%t A156561 Floor[Fibonacci[2*Range[0,30]+1]/9] (* or *) LinearRecurrence[{4,-4,1,0,0,-1,4,-4,1},{0,0,0,1,3,9,25,67,177},31] (* _Harvey P. Dale_, Jun 06 2016 *)
%Y A156561 Cf. A069403.
%K A156561 nonn
%O A156561 0,5
%A A156561 _Paul Curtz_, Feb 10 2009
%E A156561 Edited and extended by _R. J. Mathar_, Jan 23 2009, Feb 23 2009