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 A168457 #24 Dec 27 2024 13:54:18
%S A168457 2,12,12,22,22,32,32,42,42,52,52,62,62,72,72,82,82,92,92,102,102,112,
%T A168457 112,122,122,132,132,142,142,152,152,162,162,172,172,182,182,192,192,
%U A168457 202,202,212,212,222,222,232,232,242,242,252,252,262,262,272,272,282
%N A168457 a(n) = (10*n + 5*(-1)^n - 1)/2.
%H A168457 Vincenzo Librandi, <a href="/A168457/b168457.txt">Table of n, a(n) for n = 1..1000</a>
%H A168457 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1 ).
%F A168457 a(n) = 10*n - a(n-1) - 6 for n>1, a(1)=2.
%F A168457 From _Bruno Berselli_, Sep 16 2013: (Start)
%F A168457 G.f.: 2*x*(1 + 5*x - x^2)/((1+x)*(1-x)^2).
%F A168457 a(n) = A168459(n) + 1 = 2*A168282(n).
%F A168457 a(n) = a(n-1) +a(n-2) -a(n-3). (End)
%F A168457 a(n) = 2 + 10*Floor(n/2). - _Vincenzo Librandi_, Sep 19 2013
%F A168457 E.g.f.: (1/2)*(5 - 4*exp(x) + (10*x - 1)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 22 2016
%t A168457 Table[5 n + 5 (-1)^n/2 - 1/2, {n, 60}] (* _Bruno Berselli_, Sep 16 2013 *)
%t A168457 Table[2 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[2 (1 + 5 x - x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 19 2013 *)
%t A168457 LinearRecurrence[{1,1,-1},{2,12,12},80] (* _Harvey P. Dale_, Dec 27 2024 *)
%o A168457 (Magma) [2+10*Floor(n/2): n in [1..70]]; // _Vincenzo Librandi_, Sep 19 2013
%Y A168457 Cf. A017293, A168459, A168282.
%K A168457 nonn,easy,less
%O A168457 1,1
%A A168457 _Vincenzo Librandi_, Nov 26 2009
%E A168457 New definition by _Bruno Berselli_, Sep 16 2013