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%I #15 Jul 15 2023 13:48:48
%S 1,2,3,0,5,-2,7,-4,9,-6,11,-8,13,-10,15,-12,17,-14,19,-16,21,-18,23,
%T -20,25,-22,27,-24,29,-26,31,-28,33,-30,35,-32,37,-34,39,-36,41,-38,
%U 43,-40,45,-42,47,-44,49,-46,51,-48,53,-50,55,-52,57,-54,59,-56,61,-58,63,-60,65,-62,67,-64,69,-66,71,-68,73,-70,75,-72
%N a(n+3)=a(n)+a(n+1)-a(n+2), starting with 1,2,3.
%H J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,1,1).
%F O.g.f.: (1+3x+4x^2)/((1-x)(1+x)^2). a(n)=2+(n-1)*(-1)^n. [From _R. J. Mathar_, Aug 22 2008]
%e a(4)=0 because 1+2-3=0
%t LinearRecurrence[{-1,1,1},{1,2,3},80] (* _Harvey P. Dale_, Jul 15 2023 *)
%K easy,sign
%O 0,2
%A _Gregory V. Richardson_, Oct 17 2000
%E More terms from _James A. Sellers_, Oct 18 2000
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