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 A069947 #12 Apr 25 2024 09:11:58
%S A069947 1,1,2,2,4,4,12,12,12,12,60,60,10,30,120,120,240,240,720,720,720,720,
%T A069947 7920,7920,7920,7920,7920,7920,55440,55440,11088,11088,55440,55440,
%U A069947 55440,55440,18480,55440,55440,55440,55440,55440,55440,11088,11088,11088,255024,255024
%N A069947 Denominator of Sum_{k=1..n} k/phi(k).
%D A069947 József Sándor, Dragoslav S. Mitrinovic, and Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter I, p. 29, section I.27.
%H A069947 Robert Israel, <a href="/A069947/b069947.txt">Table of n, a(n) for n = 1..10000</a>
%e A069947 1, 3, 9/2, 13/2, 31/4, 43/4, 143/12, 167/12, 185/12, ...
%p A069947 map(denom, ListTools:-PartialSums([seq(n/numtheory:-phi(n),n=1..100)]));
%p A069947 # _Robert Israel_, May 01 2018
%t A069947 Accumulate[Table[n/EulerPhi[n],{n,50}]]//Denominator (* _Harvey P. Dale_, May 24 2021 *)
%o A069947 (PARI) a(n) = denominator(sum(k = 1, n, k/eulerphi(k))); \\ _Amiram Eldar_, Apr 25 2024
%Y A069947 Cf. A068885 (numerators), A028415, A048049.
%K A069947 nonn,frac
%O A069947 1,3
%A A069947 _N. J. A. Sloane_, Jun 28 2002