Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #15 Jan 25 2020 00:40:58
%S 1,-1,4,-7,18,-38,88,-195,441,-988,2223,-4992,11220,-25208,56645,
%T -127277,285992,-642615,1443946,-3244514,7290360,-16381287,36808421,
%U -82707768,185842671,-417584688,938304280,-2108350576,4737420745,-10644887785,23918845740,-53745158519,120764274994
%N Expansion of (1-x)^(-1)/(1+2*x-x^2-x^3).
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-1, 3, 0, -1).
%F a(n) = (-1)^n*A124400(n). - _Philippe Deléham_, Dec 18 2006
%F a(n) = a(n-1) + 3*a(n-2) - a(n-4); a(0)=1, a(1)=-1, a(2)=4, a(3)=-7. - _Harvey P. Dale_, Mar 13 2013
%t CoefficientList[Series[(1-x)^(-1)/(1+2x-x^2-x^3),{x,0,40}],x] (* or *) LinearRecurrence[{-1,3,0,-1},{1,-1,4,-7},40] (* _Harvey P. Dale_, Mar 13 2013 *)
%o (PARI) Vec((1-x)^(-1)/(1+2*x-x^2-x^3)+O(x^99)) \\ _Charles R Greathouse IV_, Sep 27 2012
%K sign,easy
%O 0,3
%A _N. J. A. Sloane_, Nov 17 2002