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 A109787 #13 Mar 13 2024 19:26:03
%S A109787 1,2,3,4,21,58,151,392,1037,2718,7115,18624,48769,127682,334275,
%T A109787 875140,2291157,5998330,15703831,41113160,107635661,281793822,
%U A109787 737745803,1931443584,5056584961,13238311298,34658348931,90736735492,237551857557
%N A109787 Expansion of -(1-x-2*x^2+11*x^4-3*x^3) / ((x-1)*(x+1)*(x^2-3*x+1)*(1+x^2)).
%C A109787 Floretion Algebra Multiplication Program, FAMP Code: 4tessumseq[ + .25'i + .25i' + .25'ii' + .25'jj' + .25'kk' + .25'jk' + .25'kj' + .25e], sumtype: Y[15],inty[ * ]
%H A109787 Colin Barker, <a href="/A109787/b109787.txt">Table of n, a(n) for n = 0..1000</a>
%H A109787 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,0,1,-3,1).
%F A109787 a(n) = 3*a(n-1) - a(n-2) + a(n-4) - 3*a(n-5) + a(n-6) for n>5. - _Colin Barker_, May 16 2019
%t A109787 CoefficientList[Series[-(1-x-2x^2+11x^4-3x^3)/((x-1)(x+1)(x^2-3x+1)(1+x^2)),{x,0,40}],x] (* or *) LinearRecurrence[{3,-1,0,1,-3,1},{1,2,3,4,21,58},40] (* _Harvey P. Dale_, Jan 11 2020 *)
%o A109787 (PARI) Vec((1 - x - 2*x^2 - 3*x^3 + 11*x^4) / ((1 - x)*(1 + x)*(1 - 3*x + x^2)*(1 + x^2)) + O(x^30)) \\ _Colin Barker_, May 16 2019
%Y A109787 Cf. A111664, A111666.
%K A109787 easy,nonn
%O A109787 0,2
%A A109787 _Creighton Dement_, Aug 14 2005