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%I #28 Sep 08 2022 08:45:49
%S 3,3,9,9,15,15,21,21,27,27,33,33,39,39,45,45,51,51,57,57,63,63,69,69,
%T 75,75,81,81,87,87,93,93,99,99,105,105,111,111,117,117,123,123,129,
%U 129,135,135,141,141,147,147,153,153,159,159,165,165,171,171,177,177,183,183
%N a(n) = (3/2)*(2*n - (-1)^n - 1).
%H Vincenzo Librandi, <a href="/A168329/b168329.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1, 1, -1).
%F a(n) = 6*n - a(n-1) - 6 for n>1, a(1)=3.
%F G.f.: 3*x*(1 + x^2)/((1+x)*(1-x)^2). - _Bruno Berselli_, Nov 06 2011
%F a(n) = -a(-n+1) = 3*A109613(n-1) = A198392(n-1) - A198392(-n). - _Bruno Berselli_, Nov 06 2011 - Sep 17 2013
%F E.g.f.: (3/2)*(-1 + 2*exp(x) + (2*x - 1)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 18 2016
%t LinearRecurrence[{1,1,-1},{3,3,9},80 ] (* _Vincenzo Librandi_, Nov 15 2011 *)
%t Table[(3/2) (2 n - (-1)^n - 1), {n, 70}] (* _Bruno Berselli_, Sep 17 2013 *)
%o (Magma) [(3/2)*(2*n-(-1)^n-1): n in [1..70]] // _Vincenzo Librandi_, Nov 15 2011
%Y Cf. A016945, A109613.
%K nonn,easy,less
%O 1,1
%A _Vincenzo Librandi_, Nov 23 2009
%E New definition by _Bruno Berselli_, Sep 17 2013
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