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 A077983 #34 Sep 08 2022 08:45:08
%S A077983 1,-2,6,-17,48,-136,385,-1090,3086,-8737,24736,-70032,198273,-561346,
%T A077983 1589270,-4499505,12738896,-36066072,102109441,-289089922,818464798,
%U A077983 -2317218881,6560457280,-18573817120,52585767681,-148879626882,421504606246,-1193354233937,3378597307248
%N A077983 Expansion of 1/(1 + 2*x - 2*x^2 + x^3).
%H A077983 G. C. Greubel, <a href="/A077983/b077983.txt">Table of n, a(n) for n = 0..1000</a>
%H A077983 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-2,2,-1).
%F A077983 a(n) = (-1)^n * A077936(n). - _Ivan Neretin_, Jul 05 2015
%F A077983 a(n) = -2*a(n-1) + 2*a(n-2) - a(n-3) with a(0) = 1, a(1) = -2, a(2) = 6. - _Taras Goy_, Aug 04 2017
%t A077983 LinearRecurrence[{-2,2,-1}, {1,-2,6}, 30] (* or *) CoefficientList[ Series[1/(1+2*x-2*x^2+x^3), {x,0,30}], x] (* _G. C. Greubel_, Jun 25 2019 *)
%o A077983 (PARI) my(x='x+O('x^30)); Vec(1/(1+2*x-2*x^2+x^3)) \\ _G. C. Greubel_, Jun 25 2019
%o A077983 (Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( 1/(1+2*x-2*x^2+x^3) )); // _G. C. Greubel_, Jun 25 2019
%o A077983 (Sage) (1/(1+2*x-2*x^2+x^3)).series(x, 30).coefficients(x, sparse=False) # _G. C. Greubel_, Jun 25 2019
%o A077983 (GAP) a:=[1,-2,6];; for n in [4..30] do a[n]:=-2*a[n-1]+2*a[n-2]-a[n-3]; od; a; # _G. C. Greubel_, Jun 25 2019
%Y A077983 Cf. A078054 (first differences), A077936.
%K A077983 sign,easy
%O A077983 0,2
%A A077983 _N. J. A. Sloane_, Nov 17 2002