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%I #20 May 24 2017 09:06:06
%S 1,9,63,444,3109,21765,152355,1066488,7465417,52257921,365805447,
%T 2560638132,17924466925,125471268477,878298879339,6148092155376,
%U 43036645087633,301256515613433,2108795609294031,14761569265058220,103330984855407541,723316893987852789
%N Base-7 digits are, in order, the first n terms of the periodic sequence with initial period 1,2,0,3.
%H Colin Barker, <a href="/A037691/b037691.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (7,0,0,1,-7).
%F a(n) = 7*a(n-1) + a(n-4) - 7*a(n-5).
%F From _Colin Barker_, Dec 24 2015: (Start)
%F a(n) = 1/200*(25*(-1)^n-(6-8*i)*(-i)^n-(6+8*i)*i^n+37*7^n-50) where i=sqrt(-1).
%F G.f.: x*(1+2*x+3*x^3) / ((1-x)*(1+x)*(1-7*x)*(1+x^2)).
%F (End)
%t Table[FromDigits[PadRight[{},n,{1,2,0,3}],7],{n,30}] (* _Harvey P. Dale_, May 24 2017 *)
%o (PARI) Vec(x*(1+2*x+3*x^3)/((1-x)*(1+x)*(1-7*x)*(1+x^2)) + O(x^30)) \\ _Colin Barker_, Dec 24 2015
%K nonn,base,easy
%O 1,2
%A _Clark Kimberling_
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