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 A369471 #6 Jan 26 2024 08:35:50
%S A369471 4,24,172,1144,8056,57800,427006,3221216,24773668,193592840,
%T A369471 1534006620,12301987920,99699269740,815520435048,6725987757744,
%U A369471 55882659600320,467387108739408,3932600291539096,33269691987278258,282863688830816184
%N A369471 Number of chiral pairs of polyominoes composed of n pentagonal cells of the hyperbolic regular tiling with Schläfli symbol {5,oo}.
%C A369471 A stereographic projection of the {5,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 A369471 Malin Christensson, <a href="http://malinc.se/m/ImageTiling.php">Make hyperbolic tilings of images</a>, web page, 2019.
%F A369471 a(n) = A005038(n) - A005040(n) = (A005038(n) - A369472(n)) / 2 = A005040(n) - A369472(n).
%t A369471 p=5; 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 A369471 Polyominoes: A005038 (oriented), A005040 (unoriented), A369472 (achiral), A369315 {4,oo}.
%K A369471 easy,nonn
%O A369471 4,1
%A A369471 _Robert A. Russell_, Jan 23 2024