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 A348140 #9 Jan 01 2022 08:15:28
%S A348140 1,4,13,240,719,42372,92567,14970816,21475201,8825080100,7836127861,
%T A348140 7809130867824,4132643140079,9678967816041188,2973238691433583,
%U A348140 16000787866533953280,2798084251807349761,34017524842099233036996,3336132453587291393821,90417110945911655996319600
%N A348140 a(n) is the numerator of tan(n * arctan(1/n)).
%H A348140 Amiram Eldar, <a href="/A348140/b348140.txt">Table of n, a(n) for n = 1..387</a>
%F A348140 Lim_{n->oo} a(n)/A348141(n) = tan(1) (A049471).
%e A348140 The fractions begin with 1, 4/3, 13/9, 240/161, 719/475, 42372/27755, 92567/60319, 14970816/9722113, 21475201/13913289, 8825080100/5707904499, ...
%t A348140 f[n_] := Module[{s = 1/n}, Do[s = (s + 1/n)/(1 - s/n), {k, 1, n - 1}]; s]; Numerator @ Array[f, 20]
%Y A348140 Cf. A049471, A348131, A348132, A348141 (denominators).
%K A348140 nonn,frac
%O A348140 1,2
%A A348140 _Amiram Eldar_, Oct 02 2021