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 A168401 #22 Mar 04 2024 01:12:29
%S A168401 4,13,13,22,22,31,31,40,40,49,49,58,58,67,67,76,76,85,85,94,94,103,
%T A168401 103,112,112,121,121,130,130,139,139,148,148,157,157,166,166,175,175,
%U A168401 184,184,193,193,202,202,211,211,220,220,229,229,238,238,247,247,256,256
%N A168401 a(n) = 4 + 9*floor(n/2).
%H A168401 Vincenzo Librandi, <a href="/A168401/b168401.txt">Table of n, a(n) for n = 1..1000</a>
%H A168401 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A168401 a(n) = 9*n - a(n-1) - 1, with n > 1, a(1)=4.
%F A168401 G.f.: x*(4 + 9*x - 4*x^2)/((1+x)*(x-1)^2). - _Vincenzo Librandi_, Sep 18 2013
%F A168401 a(n) = a(n-1) + a(n-2) - a(n-3). - _Vincenzo Librandi_, Sep 18 2013
%F A168401 E.g.f.: (1/4)*(9 - 16*exp(x) + (7 + 18*x)*exp(2*x))*exp(-x). - _G. C. Greubel_, Jul 21 2016
%t A168401 Table[4 + 9 Floor[n/2], {n, 60}] (* _Vincenzo Librandi_, Sep 18 2013 *)
%o A168401 (Magma) [4+9*Floor(n/2): n in [1..60]]; // _Bruno Berselli_, Sep 18 2013
%o A168401 (PARI) a(n)=n\2*9 + 4 \\ _Charles R Greathouse IV_, Jul 21 2016
%Y A168401 Cf. A017209.
%K A168401 nonn,easy
%O A168401 1,1
%A A168401 _Vincenzo Librandi_, Nov 25 2009
%E A168401 New definition by _Vincenzo Librandi_ Sep 18 2013