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 A348132 #18 Mar 31 2022 12:46:28
%S A348132 1,5,9,353,275,66637,18571,24405761,2215269,14712104501,411625181,
%T A348132 13218256749601,109949704423,16565151205544957,39931933598775,
%U A348132 27614800115689879553,18928981513351817,59095217374989483261925,11350851717672992089,157904201452248753415276001
%N A348132 a(n) is the denominator of the relativistic sum of n velocities of 1/n, in units where the speed of light is 1.
%H A348132 Amiram Eldar, <a href="/A348132/b348132.txt">Table of n, a(n) for n = 1..387</a>
%H A348132 Wikipedia, <a href="https://en.wikipedia.org/wiki/Velocity-addition_formula">Velocity-addition formula</a>.
%F A348132 a(2n-1) = n^(2n-1) + (n-1)^(2n-1) and a(2n) = ((2n+1)^(2n) + (2n-1)^(2n)) / 2. - _Thomas Ordowski_, Feb 12 2022
%e A348132 For n = 2, the sum of two velocities of 1/2 is (1/2 + 1/2)/(1 + (1/2)*(1/2)) = 4/5, thus a(2) = 5.
%t A348132 f[n_] := Module[{s = 1/n}, Do[s = (s + 1/n)/(1 + s/n), {k, 1, n - 1}]; s]; Denominator @ Array[f, 20]
%Y A348132 Cf. A348051, A348052, A348131 (numerators).
%K A348132 nonn,frac
%O A348132 1,2
%A A348132 _Amiram Eldar_, Oct 01 2021