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%I A202012 #30 Apr 10 2024 04:36:04
%S A202012 1,1,3,6,11,21,39,72,133,245,451,830,1527,2809,5167,9504,17481,32153,
%T A202012 59139,108774,200067,367981,676823,1244872,2289677,4211373,7745923,
%U A202012 14246974,26204271,48197169,88648415,163049856
%N A202012 Expansion of (1-x+x^2)/((1-x)(1-x-x^2-x^3)).
%C A202012 Antidiagonal sums of triangle T(n,k) = A104040(n,k)*(-1)^floor(k/2). - _Philippe Deléham_, Dec 11 2011
%H A202012 Harvey P. Dale, <a href="/A202012/b202012.txt">Table of n, a(n) for n = 0..1000</a>
%H A202012 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,0,-1).
%F A202012 a(n) = 2*a(n-1) - a(n-4), n>3.
%F A202012 a(n) = A008937(n-1) - A008937(n) + A008937(n+1). - _R. J. Mathar_, Dec 10 2011
%F A202012 a(n+1)-a(n) = A081172(n+2). - _Philippe Deléham_, Dec 11 2011
%t A202012 CoefficientList[Series[(1-x+x^2)/((1-x)(1-x-x^2-x^3)),{x,0,40}],x] (* or *) LinearRecurrence[{2,0,0,-1},{1,1,3,6},40] (* _Harvey P. Dale_, Apr 21 2014 *)
%Y A202012 Cf. A008937, A081172, A104040.
%K A202012 easy,nonn
%O A202012 0,3
%A A202012 _Philippe Deléham_, Dec 08 2011

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