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 A332422 #5 Feb 13 2020 02:53:45
%S A332422 0,1,-2,1,3,-1,-4,1,-2,4,5,-1,-6,-3,1,1,7,-1,-8,4,-6,6,9,-1,3,-5,-2,
%T A332422 -3,-10,2,11,1,3,8,-1,-1,-12,-7,-8,4,13,-5,-14,6,1,10,15,-1,-4,4,5,-5,
%U A332422 -16,-1,8,-3,-10,-9,17,2,-18,12,-6,1,-3,4,19,8,7,0,-20,-1
%N A332422 If n = Product (p_j^k_j) then a(n) = Sum ((-1)^(pi(p_j) + 1) * pi(p_j)), where pi = A000720.
%C A332422 Sum of odd indices of distinct prime factors of n minus the sum of even indices of distinct prime factors of n.
%H A332422 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%F A332422 G.f.: Sum_{k>=1} (-1)^(k + 1) * k * x^prime(k) / (1 - x^prime(k)).
%e A332422 a(66) = a(2 * 3 * 11) = a(prime(1) * prime(2) * prime(5)) = 1 - 2 + 5 = 4.
%t A332422 a[n_] := Plus @@ ((-1)^(PrimePi[#[[1]]] + 1) PrimePi[#[[1]]] & /@ FactorInteger[n]); Table[a[n], {n, 1, 72}]
%t A332422 nmax = 72; CoefficientList[Series[Sum[(-1)^(k + 1) k x^Prime[k]/(1 - x^Prime[k]), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%Y A332422 Cf. A000720, A002129, A071321, A112798, A066328, A195017, A316524, A325699, A332423.
%K A332422 sign
%O A332422 1,3
%A A332422 _Ilya Gutkovskiy_, Feb 12 2020