This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A166539 #35 Aug 04 2024 20:19:38
%S A166539 2,8,7,13,12,18,17,23,22,28,27,33,32,38,37,43,42,48,47,53,52,58,57,63,
%T A166539 62,68,67,73,72,78,77,83,82,88,87,93,92,98,97,103,102,108,107,113,112,
%U A166539 118,117,123,122,128,127,133,132,138,137,143,142,148,147,153,152,158
%N A166539 a(n) = (10*n + 7*(-1)^n + 5)/4.
%H A166539 Vincenzo Librandi, <a href="/A166539/b166539.txt">Table of n, a(n) for n = 1..1000</a>
%H A166539 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A166539 a(n) = 5*n - a(n-1), n>=2.
%F A166539 From _Harvey P. Dale_, Jun 29 2011: (Start)
%F A166539 a(n) = a(n-1) + a(n-2) - a(n-3), n>=4.
%F A166539 G.f.: x*(2+3*x*(2-x))/((1-x)^2*(1+x)). (End)
%F A166539 From _G. C. Greubel_, May 16 2016: (Start)
%F A166539 E.g.f.: (1/4)*(5*(1 + 2*x)*exp(x) + 7*exp(-x) - 12).
%F A166539 a(n) = a(n-1) + a(n-2) - a(n-3). (End)
%F A166539 Sum_{n>=1} (-1)^(n+1)/a(n) = 1/3 + sqrt((5-2*sqrt(5))/5)*Pi/5. - _Amiram Eldar_, Feb 24 2023
%F A166539 a(n) = A166520(n) - (-1)^n. - _G. C. Greubel_, Aug 04 2024
%t A166539 RecurrenceTable[{a[1]==2,a[n]==5n-a[n-1]},a[n],{n,70}] (* or *) LinearRecurrence[{1,1,-1},{2,8,7},70] (* _Harvey P. Dale_, Jun 29 2011 *)
%o A166539 (Magma) [5*n/2 + (5+7*(-1)^n)/4: n in [1..70]]; // _Vincenzo Librandi_, May 15 2013
%o A166539 (SageMath)
%o A166539 def A166539(n): return (5*n - 1 + 7*((n+1)%2))//2
%o A166539 [A166539(n) for n in range(1, 101)] # _G. C. Greubel_, Aug 04 2024
%Y A166539 Cf. A166519, A166520, A166521, A166522, A166523, A166524, A166525, A166526.
%K A166539 nonn,easy
%O A166539 1,1
%A A166539 _Vincenzo Librandi_, Oct 16 2009