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%I #26 Sep 08 2022 08:45:49
%S 7,7,17,17,27,27,37,37,47,47,57,57,67,67,77,77,87,87,97,97,107,107,
%T 117,117,127,127,137,137,147,147,157,157,167,167,177,177,187,187,197,
%U 197,207,207,217,217,227,227,237,237,247,247,257,257,267,267,277,277,287
%N a(n) = 7 + 10*floor((n-1)/2).
%H Vincenzo Librandi, <a href="/A168458/b168458.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) = 10*n - a(n-1) - 6, with n>1, a(1)=7.
%F G.f.: x*(7 + 3*x^2)/((1+x)*(x-1)^2). - _Vincenzo Librandi_, Sep 19 2013
%F a(n) = a(n-1) +a(n-2) -a(n-3). - _Vincenzo Librandi_, Sep 19 2013
%F From _G. C. Greubel_, Jul 23 2016: (Start)
%F a(n) = (10*n - 5*(-1)^n - 1)/2.
%F E.g.f.: (1/2)*(-5 + 6*exp(x) + (10*x - 1)*exp(2*x))*exp(-x). (End)
%p A168458:=n->7 + 10*floor((n-1)/2); seq(A168458(k), k=1..100); # _Wesley Ivan Hurt_, Nov 08 2013
%t Table[7 + 10 Floor[(n - 1)/2], {n, 70}] (* or *) CoefficientList[Series[(7 + 3 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 19 2013 *)
%t LinearRecurrence[{1,1,-1},{7,7,17},60] (* _Harvey P. Dale_, Apr 12 2018 *)
%o (Magma) [7+10*Floor((n-1)/2): n in [1..70]]; // _Vincenzo Librandi_ Sep 19 2013
%Y Cf. A017353.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Nov 26 2009
%E New definition by _Vincenzo Librandi_, Sep 19 2013
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