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 A168376 a(n) = (14*n - 7*(-1)^n - 9)/4. 2

%I

%S 3,3,10,10,17,17,24,24,31,31,38,38,45,45,52,52,59,59,66,66,73,73,80,

%T 80,87,87,94,94,101,101,108,108,115,115,122,122,129,129,136,136,143,

%U 143,150,150,157,157,164,164,171,171,178,178,185,185,192,192,199,199,206

%N a(n) = (14*n - 7*(-1)^n - 9)/4.

%H Vincenzo Librandi, <a href="/A168376/b168376.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).

%F a(n) = 7*n - a(n-1) - 8, with n>1, a(1)=3.

%F a(n) = A168331(n-1), n>1. - _R. J. Mathar_, Nov 25 2009

%F G.f.: x*(3 + 4*x^2)/((1+x) * (x-1)^2). - _R. J. Mathar_, Nov 25 2009

%F a(n) = 3 + 7*floor((n-1)/2). - _Bruno Berselli_, Sep 18 2013

%F From _G. C. Greubel_, Jul 19 2016: (Start)

%F E.g.f.: (1/4)*(-7 + 16*exp(x) + (14*x - 9)*exp(2*x))*exp(-x).

%F a(n) = a(n-1) + a(n-2) - a(n-3). (End)

%t Table[7 n/2 - (7 (-1)^n + 9)/4, {n, 60}] (* _Bruno Berselli_, Sep 17 2013 *)

%t CoefficientList[Series[(3 + 4 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 17 2013 *)

%o (MAGMA) [n eq 1 select 3 else 7*n-Self(n-1)-8: n in [1..70]]; // _Vincenzo Librandi_, Sep 17 2013

%o (PARI) a(n)=(14*n-7*(-1)^n-9)/4 \\ _Charles R Greathouse IV_, Jul 19 2016

%Y Cf. A168331.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Nov 24 2009

%E Definition rewritten using Mathar's formula by _Bruno Berselli_, Sep 17 2013

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Last modified August 23 13:53 EDT 2019. Contains 326227 sequences. (Running on oeis4.)