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 A168420 #25 Mar 04 2024 01:13:20
%S A168420 4,14,14,24,24,34,34,44,44,54,54,64,64,74,74,84,84,94,94,104,104,114,
%T A168420 114,124,124,134,134,144,144,154,154,164,164,174,174,184,184,194,194,
%U A168420 204,204,214,214,224,224,234,234,244,244,254,254,264,264,274,274,284
%N A168420 a(n) = 4 + 10*floor(n/2).
%H A168420 Vincenzo Librandi, <a href="/A168420/b168420.txt">Table of n, a(n) for n = 1..1000</a>
%H A168420 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A168420 a(n) = 10*n - a(n-1) - 2, with n>1, a(1)=4.
%F A168420 G.f.: 2*x*(2 + 5*x - 2*x^2)/((1+x)*(x-1)^2). - _Vincenzo Librandi_, Sep 19 2013
%F A168420 a(n) = a(n-1) +a(n-2) -a(n-3). - _Vincenzo Librandi_, Sep 19 2013
%F A168420 a(n) = 2*A168278(n). - _Bruno Berselli_, Sep 19 2013
%F A168420 E.g.f.: (1/2)*(5 - 8*exp(x) + (10*x + 3)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 22 2016
%t A168420 Table[4 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[(4 + 10 x - 4 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* _Vincenzo Librandi_, Sep 19 2013 *)
%o A168420 (Magma) [4+10*Floor(n/2): n in [1..70]]; // _Vincenzo Librandi_, Sep 19 2013
%Y A168420 Cf. A017317, A168278.
%K A168420 nonn,easy,less
%O A168420 1,1
%A A168420 _Vincenzo Librandi_, Nov 25 2009
%E A168420 New definition by _Vincenzo Librandi_, Sep 19 2013