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 A117791 #27 Sep 08 2022 08:45:24
%S A117791 1,1,2,3,4,6,9,13,20,30,45,68,102,153,230,345,518,778,1168,1754,2634,
%T A117791 3955,5939,8918,13391,20108,30194,45339,68081,102230,153508,230507,
%U A117791 346128,519744,780445,1171912,1759737,2642412,3967832,5958076,8946616,13434192
%N A117791 Expansion of 1/(1 - x - x^2 + x^4 - x^6).
%H A117791 G. C. Greubel, <a href="/A117791/b117791.txt">Table of n, a(n) for n = 0..1000</a>
%H A117791 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,0,-1,0,1).
%F A117791 a(n) = a(n-1) + a(n-2) - a(n-4) + a(n-6). - _Ilya Gutkovskiy_, Nov 16 2016
%p A117791 seq(coeff(series(1/(1 -x -x^2 +x^4 -x^6), x, n+1), x, n), n = 0..50); # _G. C. Greubel_, Dec 05 2019
%t A117791 CoefficientList[Series[1/(1 -x -x^2 +x^4 -x^6), {x, 0, 50}], x]
%o A117791 (PARI) Vec(1/(1 -x -x^2 +x^4 -x^6)+O(x^50)) \\ _Charles R Greathouse IV_, Sep 23 2012
%o A117791 (Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!(1/(1-x-x^2+x^4-x^6))); // _G. C. Greubel_, Nov 03 2018
%o A117791 (Sage)
%o A117791 def A117791_list(prec):
%o A117791 P.<x> = PowerSeriesRing(ZZ, prec)
%o A117791 return P( 1/(1 -x -x^2 +x^4 -x^6) ).list()
%o A117791 A117791_list(50) # _G. C. Greubel_, Dec 05 2019
%Y A117791 Cf. A029826, A143419, A143438, A143472, A143619, A143644, A147663, A173908, A173911, A173924, A173925, A174522, A175740, A175772, A175773, A175782, A181600, A204631, A225391, A225393, A225394, A225482, A225499.
%K A117791 nonn,easy
%O A117791 0,3
%A A117791 _Roger L. Bagula_, Apr 15 2006
%E A117791 Edited by _N. J. A. Sloane_, Nov 08 2006