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 A168456 #26 Sep 08 2022 08:45:49
%S A168456 8,8,18,18,28,28,38,38,48,48,58,58,68,68,78,78,88,88,98,98,108,108,
%T A168456 118,118,128,128,138,138,148,148,158,158,168,168,178,178,188,188,198,
%U A168456 198,208,208,218,218,228,228,238,238,248,248,258,258,268,268,278,278,288
%N A168456 a(n) = (10*n - 5*(-1)^n + 1)/2.
%H A168456 Vincenzo Librandi, <a href="/A168456/b168456.txt">Table of n, a(n) for n = 1..1000</a>
%H A168456 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A168456 a(n) = 10*n - a(n-1) - 4, with n>1, a(1)=8.
%F A168456 a(1)=8, a(2)=8, a(3)=18; for n>3, a(n) = a(n-1) + a(n-2) - a(n-3). - _Harvey P. Dale_, Aug 02 2013
%F A168456 From _R. J. Mathar_, Aug 06 2013: (Start)
%F A168456 G.f. 2*x*(4 + x^2) / ( (1+x)*(x-1)^2 ).
%F A168456 a(n) = 2*A168280(n). (End)
%F A168456 a(n) = 8 + 10*floor((n-1)/2). - _Vincenzo Librandi_, Sep 19 2013
%F A168456 E.g.f.: (1/2)*(-5 + 4*exp(x) + (10*x + 1)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 22 2016
%t A168456 RecurrenceTable[{a[1]==8,a[n]==10n-a[n-1]-4},a,{n,60}] (* or *) LinearRecurrence[ {1,1,-1},{8,8,18},60] (* or *) With[{c=NestList[ 10+#&,8,30]},Riffle[c,c]] (* _Harvey P. Dale_, Aug 02 2013 *)
%t A168456 Table[8 + 10 Floor[(n - 1)/2], {n, 70}] (* or *) CoefficientList[Series[2 (4 + x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 19 2013 *)
%o A168456 (Magma) [8+10*Floor((n-1)/2): n in [1..70]]; // _Vincenzo Librandi_, Sep 19 2013
%Y A168456 Cf. A168280, A017365.
%K A168456 nonn,easy
%O A168456 1,1
%A A168456 _Vincenzo Librandi_, Nov 26 2009