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A168411 a(n) = 7 + 9*floor((n-1)/2). 1

%I #22 Mar 04 2024 01:12:44

%S 7,7,16,16,25,25,34,34,43,43,52,52,61,61,70,70,79,79,88,88,97,97,106,

%T 106,115,115,124,124,133,133,142,142,151,151,160,160,169,169,178,178,

%U 187,187,196,196,205,205,214,214,223,223,232,232,241,241,250,250,259

%N a(n) = 7 + 9*floor((n-1)/2).

%H Vincenzo Librandi, <a href="/A168411/b168411.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) = 9*n - a(n-1) - 4, with n>1, a(1)=7.

%F G.f.: x*(7 + 2*x^2) / ( (1+x)*(x-1)^2 ). - _R. J. Mathar_, Jul 10 2011

%F a(n) = a(n-1) +a(n-2) -a(n-3). - _Vincenzo Librandi_, Sep 19 2013

%F E.g.f.: (1/4)*(-9 + 8*exp(x) + (18*x + 1)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 22 2016

%t Table[7 + 9 Floor[(n - 1)/2], {n, 70}] (* or *) CoefficientList[Series[(7 + 2 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 19 2013 *)

%o (Magma) [7+9*Floor((n-1)/2): n in [1..70]]; // _Vincenzo Librandi_, Sep 19 2013

%Y Cf. A017245.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Nov 25 2009

%E New definition by _Vincenzo Librandi_, Sep 19 2013

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)