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 A111644 #10 Mar 11 2024 20:53:54
%S A111644 1,-6,29,-124,501,-1962,7545,-28696,108393,-407662,1528981,-5724500,
%T A111644 21408221,-80003026,298832369,-1115878064,4166011601,-15551383382,
%U A111644 58047283725,-216656490156,808623915973,-3017948390522,11263433318761,-42036421446600,156883789264441
%N A111644 Expansion of -(1+x^2)/((x^2+4*x+1)*(x^2-2*x-1)).
%C A111644 In reference to the program code, the sequence of Pell numbers A000126 is given by 1kbaseseq[C*J]. A001353 is 1ibaseiseq[C*J].
%C A111644 Floretion Algebra Multiplication Program, FAMP Code: 1basejseq[C*J] with C = - 'j + 'k - j' + k' - 'ii' - 'ij' - 'ik' - 'ji' - 'ki' and J = + j' + k' + 1.5'ii' + .5'jj' + .5'kk' + .5e
%H A111644 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-6,-8,2,1).
%F A111644 a(0)=1, a(1)=-6, a(2)=29, a(3)=-124, a(n)=-6*a(n-1)-8*a(n-2)+ 2*a(n-3)+ a(n-4). - _Harvey P. Dale_, May 23 2015
%t A111644 CoefficientList[Series[-(1+x^2)/((x^2+4x+1)(x^2-2x-1)),{x,0,40}],x] (* or *) LinearRecurrence[{-6,-8,2,1},{1,-6,29,-124},40] (* _Harvey P. Dale_, May 23 2015 *)
%Y A111644 Cf. A111639, A111640, A111641, A111642, A111643, A111645, A000126.
%K A111644 easy,sign
%O A111644 0,2
%A A111644 _Creighton Dement_, Aug 10 2005