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 A018839 #24 Jan 27 2018 15:30:27
%S A018839 1,8,32,88,192,304,372,416,472,540,608,676,744,812,880,948,1016,1084,
%T A018839 1152,1220,1288,1356,1424,1492,1560,1628,1696,1764,1832,1900,1968,
%U A018839 2036,2104,2172,2240,2308,2376,2444,2512,2580,2648,2716,2784,2852,2920,2988
%N A018839 Squares on infinite chessboard at n moves from center using a {2,3} fairy knight.
%H A018839 Vincenzo Librandi, <a href="/A018839/b018839.txt">Table of n, a(n) for n = 0..1000</a>
%H A018839 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A018839 For n >= 8, a(n) = 68n - 72. - _David W. Wilson_
%F A018839 G.f.: (x+1)*(12*x^8 - 24*x^6 - 20*x^5 + 28*x^4 + 20*x^3 + 12*x^2 + 5*x + 1)/(x-1)^2. - _Colin Barker_, Oct 04 2012
%t A018839 CoefficientList[Series[(x + 1) (12 x^8 - 24 x^6 - 20 x^5 + 28 x^4 + 20 x^3 + 12 x^2 + 5*x + 1)/(x - 1)^2, {x, 0, 50}], x] (* _Vincenzo Librandi_, Oct 16 2013 *)
%Y A018839 Cf. A297740 (partial sums).
%K A018839 nonn,easy
%O A018839 0,2
%A A018839 _Marc LeBrun_