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 A336705 #22 Sep 01 2023 04:01:38
%S A336705 1,3,7,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,
%T A336705 96,100,104,108,112,116,120,124,128,132,136,140,144,148,152,156,160,
%U A336705 164,168,172,176,180,184,188,192,196,200,204,208,212,216,220,224,228
%N A336705 Coordination sequence for the half-Manhattan lattice.
%C A336705 In the half-Manhattan lattice, E-W streets run alternately E and W, but N-S streets are two way.
%H A336705 Paolo Xausa, <a href="/A336705/b336705.txt">Table of n, a(n) for n = 0..10000</a>
%H A336705 Sean A. Irvine, <a href="/A336705/a336705.png">Illustration of a(0) to a(7)</a>
%H A336705 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A336705 G.f.: (1+x) * (1+2*x^2-x^3) / (1-x)^2.
%F A336705 a(n) = 4*n, n >= 3.
%t A336705 LinearRecurrence[{2,-1},{1,3,7,12,16},100] (* _Paolo Xausa_, Sep 01 2023 *)
%Y A336705 Cf. A336627 (Manhattan lattice), A008574 (square lattice), A336726 (self-avoiding walks), A336742 (self-avoiding cycles).
%K A336705 nonn
%O A336705 0,2
%A A336705 _Sean A. Irvine_, Jul 31 2020