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 A333698 #9 Apr 03 2020 12:04:52
%S A333698 0,1,1,1,2,2,2,1,1,3,4,2,2,3,3,1,6,2,4,3,3,5,6,2,2,3,1,3,4,4,10,1,5,7,
%T A333698 4,2,4,5,3,3,12,4,6,5,3,7,8,2,2,3,7,3,8,2,6,3,5,5,16,4,6,11,3,1,4,6,
%U A333698 18,7,7,5,8,2,12,5,3,5,6,4,10,3,1,13,22,4,8
%N A333698 G.f.: Sum_{k>=1} phi(k) * x^prime(k) / (1 - x^prime(k)).
%H A333698 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%F A333698 If n = Product (p_j^k_j) then a(n) = Sum (phi(pi(p_j))).
%e A333698 a(63) = a(3^2 * 7) = a(prime(2)^2 * prime(4)) = A000010(2) + A000010(4) = 1 + 2 = 3.
%t A333698 nmax = 85; CoefficientList[Series[Sum[EulerPhi[k] x^Prime[k]/(1 - x^Prime[k]), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%t A333698 a[n_] := Plus @@ (EulerPhi[PrimePi[#[[1]]]] & /@ FactorInteger[n]); Table[a[n], {n, 85}]
%o A333698 (PARI) a(n) = my(f=factor(n)); sum(k=1, #f~, eulerphi(primepi(f[k,1]))); \\ _Michel Marcus_, Apr 03 2020
%Y A333698 Cf. A000010, A000720, A055631, A066328, A067240.
%K A333698 nonn
%O A333698 1,5
%A A333698 _Ilya Gutkovskiy_, Apr 02 2020