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 A098498 #13 Jul 17 2024 18:58:19
%S A098498 1,5,23,60,110,172,248,338,442,560,692,838,998,1172,1360,1562,1778,
%T A098498 2008,2252,2510,2782,3068,3368,3682,4010,4352,4708,5078,5462,5860,
%U A098498 6272,6698,7138,7592,8060,8542,9038,9548,10072,10610,11162,11728,12308,12902,13510
%N A098498 Number of squares on infinite half chessboard at <=n knight moves from a fixed point on the edge.
%H A098498 Paolo Xausa, <a href="/A098498/b098498.txt">Table of n, a(n) for n = 0..10000</a>
%H A098498 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A098498 a(n) = 7*n^2 - n + 2, for n>3.
%F A098498 a(n) = 3*a(n-1)-3*a(n-2)+a(n-3) for n>6. G.f.: -(2*x^6 -x^5 -6*x^4 +5*x^3 +11*x^2 +2*x +1) / (x -1)^3. - _Colin Barker_, Jul 14 2013
%e A098498 5 squares are reachable after 1 move, from these you can reach 18 new squares more, so a(1)=5 and a(2)=23.
%t A098498 LinearRecurrence[{3, -3, 1}, {1, 5, 23, 60, 110, 172, 248}, 50] (* _Paolo Xausa_, Jul 17 2024 *)
%Y A098498 See A018836 (unbounded), A098499 (diagonal halfplane), A098500 (quadrant), A098501 (octant).
%K A098498 nonn,easy
%O A098498 0,2
%A A098498 _Ralf Stephan_, Sep 15 2004
%E A098498 More terms from _Colin Barker_, Jul 14 2013