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 A098502 #37 Apr 04 2025 03:13:51
%S A098502 12,28,44,60,76,92,108,124,140,156,172,188,204,220,236,252,268,284,
%T A098502 300,316,332,348,364,380,396,412,428,444,460,476,492,508,524,540,556,
%U A098502 572,588,604,620,636,652,668,684,700,716,732,748,764,780,796,812,828,844
%N A098502 a(n) = 16*n - 4.
%C A098502 For n > 3, the number of squares on the infinite 4-column chessboard at <= n knight moves from any fixed start point.
%H A098502 Vincenzo Librandi, <a href="/A098502/b098502.txt">Table of n, a(n) for n = 1..5000</a>
%H A098502 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>.
%H A098502 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%H A098502 <a href="/index/Se#sequences_which_agree_for_a_long_time">Index entries for sequences which agree for a long time but are different</a>.
%F A098502 G.f.: 4*x*(3+x)/(1-x)^2. - _Colin Barker_, Jan 09 2012
%F A098502 Sum_{n>=1} (-1)^(n+1)/a(n) = (Pi + log(3 - 2*sqrt(2)))/(16*sqrt(2)). - _Amiram Eldar_, Sep 01 2024
%F A098502 From _Elmo R. Oliveira_, Apr 03 2025: (Start)
%F A098502 E.g.f.: 4*(exp(x)*(4*x - 1) + 1).
%F A098502 a(n) = 2*a(n-1) - a(n-2) for n > 2.
%F A098502 a(n) = 4*A004767(n-1) = 2*A017137(n-1) = A017113(2*n-1). (End)
%t A098502 Range[12, 1000, 16] (* _Vladimir Joseph Stephan Orlovsky_, May 31 2011 *)
%o A098502 (Magma) [16*n - 4: n in [1..60]]; // _Vincenzo Librandi_, Jul 24 2011
%o A098502 (PARI) a(n)=16*n-4 \\ _Charles R Greathouse IV_, Jul 10 2016
%Y A098502 Cf. A004767, A008590, A017113, A017137, A017629, A098498, A158953.
%K A098502 nonn,easy
%O A098502 1,1
%A A098502 _Ralf Stephan_, Sep 15 2004