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 A348141 #8 Jan 01 2022 08:15:24
%S A348141 1,3,9,161,475,27755,60319,9722113,13913289,5707904499,5061910249,
%T A348141 5039646554593,2665025213747,6237995487261915,1915304790146175,
%U A348141 10303367499652761601,1801181048868783377,21891769059478538933603,2146451844926024801801,58162468900440912135124001
%N A348141 a(n) is the denominator of tan(n * arctan(1/n)).
%H A348141 Amiram Eldar, <a href="/A348141/b348141.txt">Table of n, a(n) for n = 1..387</a>
%t A348141 f[n_] := Module[{s = 1/n}, Do[s = (s + 1/n)/(1 - s/n), {k, 1, n - 1}]; s]; Denominator @ Array[f, 20]
%Y A348141 Cf. A348131, A348132, A348140 (numerators).
%K A348141 nonn,frac
%O A348141 1,2
%A A348141 _Amiram Eldar_, Oct 02 2021