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%I #19 Sep 08 2022 08:44:52
%S 2,9,38,154,617,2470,9882,39529,158118,632474,2529897,10119590,
%T 40478362,161913449,647653798,2590615194,10362460777,41449843110,
%U 165799372442,663197489769,2652789959078,10611159836314,42444639345257
%N Base 4 digits are, in order, the first n terms of the periodic sequence with initial period 2,1,2.
%H Vincenzo Librandi, <a href="/A037569/b037569.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 (4,0,1,-4).
%F G.f.: x*(2+x+2*x^2) / ((x-1)*(4*x-1)*(1+x+x^2)). - _R. J. Mathar_, Nov 21 2011
%F a(n) = 4*(n-1) + a(n-3) - 4*a(n-4). - _Vincenzo Librandi_, Jun 17 2012
%t With[{c=PadRight[{},30,{2,1,2}]},Table[FromDigits[Take[c,n],4],{n,30}]] (* _Harvey P. Dale_, Nov 06 2011 *)
%t LinearRecurrence[{4,0,1,-4},{2,9,38,154},40] (* _Vincenzo Librandi_, Jun 17 2012 *)
%o (Magma) I:=[2, 9, 38, 154]; [n le 4 select I[n] else 4*Self(n-1)+Self(n-3)-4*Self(n-4): n in [1..30]]; // _Vincenzo Librandi_, Jun 17 2012
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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