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 A369473 #6 Jan 26 2024 08:36:27
%S A369473 7,50,448,3810,34200,314655,2982040,28897440,285577500,2868769045,
%T A369473 29227672960,301429078080,3141983233130,33059729519325,
%U A369473 350763428176480,3749420512083472,40348040467611800,436827334389425980
%N A369473 Number of chiral pairs of polyominoes composed of n hexagonal cells of the hyperbolic regular tiling with Schläfli symbol {6,oo}.
%C A369473 A stereographic projection of the {6,oo} tiling on the Poincaré disk can be obtained via the Christensson link. Each member of a chiral pair is a reflection but not a rotation of the other.
%H A369473 Malin Christensson, <a href="http://malinc.se/m/ImageTiling.php">Make hyperbolic tilings of images</a>, web page, 2019.
%F A369473 a(n) = A221184(n-1) - A004127(n) = (A221184(n-1) - A143546(n)) / 2 = A004127(n) - A143546(n).
%t A369473 p=6; Table[(Binomial[(p-1)n, n]/(((p-2)n+1)((p-2)n+2))-If[OddQ[n], If[OddQ[p], Binomial[(p-1)n/2, (n-1)/2]/n, (p+1)Binomial[((p-1)n-1)/2, (n-1)/2]/((p-2)n+2)-Binomial[((p-1)n+1)/2, (n-1)/2]/((p-1)n+1)], Binomial[(p-1)n/2, n/2]/((p-2)n+2)]+DivisorSum[GCD[p, n-1], EulerPhi[#]Binomial[((p-1)n+1)/#, (n-1)/#]/((p-1)n+1)&, #>1&])/2, {n, 4, 30}]
%Y A369473 Polyominoes: A221184(n-1) (oriented), A004127 (unoriented), A143546 (achiral), A369471 {5,oo}.
%K A369473 easy,nonn
%O A369473 4,1
%A A369473 _Robert A. Russell_, Jan 23 2024