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 A265045 #21 Sep 23 2017 12:18:59
%S A265045 1,3,7,11,14,18,23,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,
%T A265045 96,100,104,108,112,116,120,124,128,132,136,140,144,148,152,156,160,
%U A265045 164,168,172,176,180,184,188,192,196,200,204,208,212,216,220,224,228,232
%N A265045 Coordination sequence for a 6.6.6 point in the 3-transitive tiling {4.6.6, 6.6.6, 6.6.6.6} of the plane by squares and dominoes (hexagons).
%C A265045 This tiling is 3-transitive but not 3-uniform since the polygons are not regular. It is a common floor-tiling.
%C A265045 The coordination sequences with respect to the points of types 4.6.6 (labeled "C" in the illustration), 6.6.6 ("B"), 6.6.6.6 ("A") are A265046, A265045, and A008574, respectively. The present sequence is for a "B" point.
%H A265045 Colin Barker, <a href="/A265045/b265045.txt">Table of n, a(n) for n = 0..1000</a>
%H A265045 N. J. A. Sloane, <a href="/A265045/a265045.png">A portion of the 3-transitive tiling {4.6.6, 6.6.6, 6.6.6.6}</a>
%H A265045 N. J. A. Sloane, <a href="/A265045/a265045_1.png">A portion of the 3-transitive tiling {4.6.6, 6.6.6, 6.6.6.6} showing the three types of point</a>
%H A265045 N. J. A. Sloane, <a href="/A265045/a265045_2.png">Hand-drawn illustration showing a(0) to a(10)</a>
%H A265045 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A265045 For n >= 7 all three sequences equal 4n. (For n >= 7 the n-th shell contains n-1 points in the interior of each quadrant plus 4 points on the axes.)
%F A265045 From _Colin Barker_, Jan 01 2016: (Start)
%F A265045 a(n) = 2*a(n-1)-a(n-2) for n>8.
%F A265045 a(n) = 4*n for n>6.
%F A265045 G.f.: (1+x)*(1+2*x^2-2*x^3+x^4+x^6-x^7) / (1-x)^2.
%F A265045 (End)
%t A265045 LinearRecurrence[{2,-1},{1,3,7,11,14,18,23,28,32},60] (* _Harvey P. Dale_, Sep 23 2017 *)
%o A265045 (PARI) Vec((1+x)*(1+2*x^2-2*x^3+x^4+x^6-x^7)/(1-x)^2 + O(x^100)) \\ _Colin Barker_, Jan 01 2016
%Y A265045 Cf. A008574, A265046.
%K A265045 nonn,easy
%O A265045 0,2
%A A265045 _N. J. A. Sloane_ and _Susanna Cuyler_, Dec 27 2015