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A168379 a(n) = 4*n - 2*(-1)^n + 1.

%I A168379 #25 Mar 19 2024 09:33:04
%S A168379 7,7,15,15,23,23,31,31,39,39,47,47,55,55,63,63,71,71,79,79,87,87,95,
%T A168379 95,103,103,111,111,119,119,127,127,135,135,143,143,151,151,159,159,
%U A168379 167,167,175,175,183,183,191,191,199,199,207,207,215,215,223,223,231,231
%N A168379 a(n) = 4*n - 2*(-1)^n + 1.
%H A168379 Vincenzo Librandi, <a href="/A168379/b168379.txt">Table of n, a(n) for n = 1..1000</a>
%H A168379 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A168379 a(n) = 8*n - a(n-1) - 2, with n>1, a(1)=7.
%F A168379 G.f.: x*(7 + x^2)/((1+x)*(1-x)^2). - _Vincenzo Librandi_, Sep 18 2013
%F A168379 a(n) = a(n-1) +a(n-2) -a(n-3). - _Vincenzo Librandi_, Sep 18 2013
%F A168379 a(n) = 7 + 8*floor((n-1)/2). - _Bruno Berselli_, Sep 18 2013
%F A168379 E.g.f.: (-2 + exp(x) + (4*x + 1)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 19 2016
%p A168379 A168379:=n->4*n - 2*(-1)^n + 1: seq(A168379(n), n=1..100); # _Wesley Ivan Hurt_, Apr 26 2017
%t A168379 Table[4 n - 2 (-1)^n + 1, {n, 60}] (* _Bruno Berselli_, Sep 18 2013 *)
%t A168379 CoefficientList[Series[(7 + x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 18 2013 *)
%o A168379 (Magma) [4*n -2*(-1)^n + 1: n in [1..70]]; // _Vincenzo Librandi_, Sep 18 2013
%K A168379 nonn,easy
%O A168379 1,1
%A A168379 _Vincenzo Librandi_, Nov 24 2009
%E A168379 Definition rewritten by _Vincenzo Librandi_, Sep 18 2013