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 A377322 #7 Feb 13 2025 08:30:37
%S A377322 1,4,12,28,64,148,340,780,1792,4116,9452,21708,49856,114500,262964,
%T A377322 603932,1387008,3185444,7315788,16801660,38587200,88620532,203528596,
%U A377322 467429932,1073513728,2465464116,5662259500,13004116524,29865647552,68590349988,157526673524
%N A377322 Number of cells that are a distance of n away in an order-5 hyperbolic square tiling.
%C A377322 Also known as a {4,5} tiling.
%C A377322 The formula given in the MathOverflow answer (4 * A033303) is erroneous after n=3.
%H A377322 M. Lavrov, <a href="https://math.stackexchange.com/q/2222314">Description of the order-5 square tiling of the hyperbolic plane as a graph</a>, MathOverflow
%H A377322 EC Puzzle Hunt, <a href="https://ecph.site/solution/tower-navigation">Solution: Tower Navigation</a>
%H A377322 <a href="/index/Con#coordination_sequences">Index entries for coordination sequences</a>.
%H A377322 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,2,-1).
%F A377322 G.f.: (1 + 2*x + 4*x^2 + 2*x^3 + x^4)/(1 - 2*x - 2*x^3 + x^4). - _Andrew Howroyd_, Feb 12 2025
%o A377322 (PARI) Vec((1 + 2*x + 4*x^2 + 2*x^3 + x^4)/(1 - 2*x - 2*x^3 + x^4) + O(x^31)) \\ _Andrew Howroyd_, Feb 12 2025
%Y A377322 Cf. A008574, A054888 (dual).
%K A377322 nonn,easy
%O A377322 0,2
%A A377322 _Lewis Chen_, Oct 24 2024
%E A377322 a(20) onwards from _Andrew Howroyd_, Feb 12 2025