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 A373924 #10 Sep 13 2024 15:57:23
%S A373924 1,-2,0,2,-2,0,0,0,0,4,-2,-2,0,2,2,0,-2,0,0,-2,0,4,-2,0,0,0,-2,-4,0,
%T A373924 -2,-2,-2,0,2,0,0,0,2,0,0,-2,-2,0,-2,0,4,-2,0,-2,-2,0,-2,0,4,4,2,0,2,
%U A373924 -2,0,0,4,0,2,2,0,-2,-2,0,-4,0,2,-2,0,-2,-4,0,0,0,0,2
%N A373924 a(n) = Sum_{d|n} (-1)^pi(d) * mu(n/d).
%C A373924 Möbius transform of (-1)^pi(n) (A065357).
%H A373924 Robert Israel, <a href="/A373924/b373924.txt">Table of n, a(n) for n = 1..10000</a>
%p A373924 f:= proc(n) local d; add((-1)^numtheory:-pi(d)*numtheory:-mobius(n/d),d=numtheory:-divisors(n)) end proc:
%p A373924 map(f, [$1..100]); # _Robert Israel_, Sep 13 2024
%t A373924 Table[DivisorSum[n, (-1)^PrimePi[#] MoebiusMu[n/#] &], {n, 100}]
%Y A373924 Cf. A000720 (pi), A008683 (mu), A065357, A373923.
%K A373924 sign
%O A373924 1,2
%A A373924 _Wesley Ivan Hurt_, Jun 22 2024