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%I #16 Jan 20 2017 11:36:58
%S 1,3,10,31,93,280,841,2523,7570,22711,68133,204400,613201,1839603,
%T 5518810,16556431,49669293,149007880,447023641,1341070923,4023212770,
%U 12069638311,36208914933,108626744800,325880234401,977640703203,2932922109610,8798766328831
%N Base-3 digits are, in order, the first n terms of the periodic sequence with initial period 1,0,1.
%H Colin Barker, <a href="/A033121/b033121.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3,0,1,-3).
%F a(n) = 3*a(n-1) + a(n-3) - 3*a(n-4).
%F G.f.: x*(1+x^2) / ((1-x)*(1-3*x)*(1+x+x^2)). - _Colin Barker_, Dec 24 2015
%t Table[FromDigits[PadRight[{},n,{1,0,1}],3],{n,30}] (* or *) LinearRecurrence[ {3,0,1,-3},{1,3,10,31},30] (* _Harvey P. Dale_, Jan 20 2017 *)
%o (PARI) Vec(x*(1+x^2)/((1-x)*(1-3*x)*(1+x+x^2)) + O(x^30)) \\ _Colin Barker_, Dec 24 2015
%K nonn,base,easy
%O 1,2
%A _Clark Kimberling_
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