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%I #26 May 01 2023 08:05:08
%S 1,1,4,7,7,10,13,13,16,19,19,22,25,25,28,31,31,34,37,37,40,43,43,46,
%T 49,49,52,55,55,58,61,61,64,67,67,70,73,73,76,79,79,82,85,85,88,91,91,
%U 94,97,97,100,103,103,106,109,109,112,115,115,118
%N Duplicate of A061891.
%H G. C. Greubel, <a href="/A168074/b168074.txt">Table of n, a(n) for n = 0..1000</a>
%F G.f.: (1+3x^2+2x^3)/((1-x)^2*(1+x+x^2)).
%F a(n) = A168075(n)/(-3)^n.
%F a(n) = A061891(n). - _Georg Fischer_, Oct 14 2018
%t LinearRecurrence[{1, 0, 1, -1}, {1, 1, 4, 7}, 50] (* _G. C. Greubel_, Jul 09 2016 *)
%t CoefficientList[Series[(1 + 3 x^2 + 2 x^3) / ((1 - x)^2 (1 + x + x^2)), {x, 0, 60}], x] (* _Vincenzo Librandi_, Jul 10 2016 *)
%o (PARI) Vec((1+3*x^2+2*x^3)/((1-x)^2*(1+x+x^2)) + O(x^70)) \\ _Michel Marcus_, Dec 03 2014
%o (Magma) I:=[1,1,4,7]; [n le 4 select I[n] else Self(n-1)+Self(n-3)-Self(n-4): n in [1..70]]; // _Vincenzo Librandi_, Jul 10 2016
%K dead
%O 0,3
%A _Paul Barry_, Nov 18 2009
%E Corrected by _R. J. Mathar_, Dec 03 2014
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