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A121311 a(0) = 1, a(1) = 2, a(2) = 5; for n >= 3, a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3).

%I A121311 #14 Jun 18 2021 06:54:57
%S A121311 1,2,5,2,-6,-5,9,13,-10,-27,6,50,11,-83,-55,122,149,-150,-326,123,625,
%T A121311 53,-1074,-555,1646,1682,-2165,-3883,2129,7730,-411,-13742,-5190,
%U A121311 21883,18521,-30435,-45594,33797,94550,-18638,-173941,-42115,287129,197418,-418955,-526662,508666,1143035,-400959
%N A121311 a(0) = 1, a(1) = 2, a(2) = 5; for n >= 3, a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3).
%H A121311 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1, -2, 1).
%F A121311 O.g.f.: -(1+x+5*x^2)/(-1+x-2*x^2+x^3) . - _R. J. Mathar_, Dec 10 2007
%t A121311 a[0] = 1; a[1] = 2; a[2] = 5; a[n_] := a[n] = a[n - 1] - 2a[n - 2] + a[n - 3]; Table[ a[n], {n, 0, 40}]
%t A121311 LinearRecurrence[{1,-2,1},{1,2,5},50] (* _Harvey P. Dale_, Dec 05 2012 *)
%Y A121311 Cf. A101399.
%K A121311 sign,easy
%O A121311 0,2
%A A121311 _Zak Seidov_, Aug 25 2006
%E A121311 Offset adapted to definition by _Georg Fischer_, Jun 18 2021