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 A146312 #39 Feb 02 2025 09:25:49
%S A146312 2,242,23762,2328482,228167522,22358088722,2190864527282,
%T A146312 214682365584962,21036680962799042,2061380051988721202,
%U A146312 201994208413931878802,19793371044513335401442,1939548368153892937462562,190055946708036994535929682,18623543229019471571583646322
%N A146312 a(n) = -cos((2*n-1)*arcsin(sqrt(3)))^2 = -1 + cosh((2*n-1)*arcsinh(sqrt(2)))^2.
%H A146312 G. C. Greubel, <a href="/A146312/b146312.txt">Table of n, a(n) for n = 1..500</a>
%H A146312 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (99,-99,1).
%F A146312 General formula: cosh((2*n-1)*arcsinh(sqrt(2)))^2 + cos((2*n-1)*arcsin(sqrt(3)))^2 = 1.
%F A146312 a(n) = A146313(n) - 1.
%F A146312 From _Colin Barker_, Oct 26 2014: (Start)
%F A146312 a(n) = 99*a(n-1) - 99*a(n-2) + a(n-3).
%F A146312 G.f.: -2*x*(x^2+22*x+1) / ((x-1)*(x^2-98*x+1)). (End)
%F A146312 a(n) = 2*A054320(n-1)^2. - _Jon E. Schoenfield_, Jun 08 2018
%t A146312 Table[Round[ -N[Cos[(2 n - 1) ArcSin[Sqrt[3]]], 300]^2], {n, 1, 50}]
%t A146312 LinearRecurrence[{99, -99, 1}, {2, 242, 23762}, 50] (* _G. C. Greubel_, Jul 03 2017 *)
%o A146312 (PARI) Vec(-2*x*(x^2+22*x+1) / ((x-1)*(x^2-98*x+1)) + O(x^100)) \\ _Colin Barker_, Oct 26 2014
%Y A146312 Cf. A054320, A146311, A146313.
%K A146312 nonn,easy
%O A146312 1,1
%A A146312 _Artur Jasinski_, Oct 29 2008
%E A146312 More terms from _Colin Barker_, Oct 26 2014