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%I #19 May 31 2020 00:53:50
%S 1,2,0,3,5,8,16,29,53,98,180,331,609,1120,2060,3789,6969,12818,23576,
%T 43363,79757,146696,269816,496269,912781,1678866,3087916,5679563,
%U 10446345,19213824,35339732,64999901,119553457,219893090
%N Tribonacci-like sequence a(n) = a(n-1) + a(n-2) + a(n-3) for n >= 3, with a(0) = 1, a(1) = 2, a(2) = 0.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1).
%F G.f.: (3 x^2-x-1)/(x^3+x^2+x-1).
%F a(n) = A275778(n) - A000073(n).
%t LinearRecurrence[{1, 1, 1}, {1, 2, 0}, 35] (* or *)
%t RecurrenceTable[{a[n] == a[n - 1] + a[n - 2] + a[n - 3], a[1] == 1, a[2] == 2, a[3] == 0}, a, {n, 35}] (* or *)
%t CoefficientList[Series[(-1 - x + 3 x^2)/(-1 + x + x^2 + x^3), {x, 0, 40}], x]
%o (PARI) a(n)=([0,1,0; 0,0,1; 1,1,1]^n*[1;2;0])[1,1] \\ _Charles R Greathouse IV_, Sep 13 2016
%Y Cf. A000073, A275778.
%K nonn,easy
%O 0,2
%A _Nicolas Bègue_, Sep 11 2016
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