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 A361984 #17 May 10 2023 04:31:29
%S A361984 1,0,-1,1,-1,0,-1,2,0,0,-1,-1,-1,0,1,4,-1,0,-1,-1,1,0,-1,-2,0,0,0,-1,
%T A361984 -1,0,-1,8,1,0,1,0,-1,0,1,-2,-1,0,-1,-1,0,0,-1,-4,0,0,1,-1,-1,0,1,-2,
%U A361984 1,0,-1,1,-1,0,0,16,1,0,-1,-1,1,0,-1,0,-1,0,0,-1,1,0,-1,-4,0,0,-1,1,1,0,1,-2,-1,0,1,-1,1,0,1,-8,-1,0,0,0
%N A361984 a(1) = 1, a(2) = 0; a(n) = Sum_{d|n, d < n} (-1)^(n/d) a(d).
%H A361984 Seiichi Manyama, <a href="/A361984/b361984.txt">Table of n, a(n) for n = 1..10000</a>
%F A361984 a(n) is multiplicative with a(2) = 0, a(2^e) = 2^(e-2) if e>1. a(p) = -1, a(p^e) = 0 if e>1, p>2.
%F A361984 G.f. A(x) satisfies -x * (1 - x) = Sum_{k>=1} (-1)^k * A(x^k).
%t A361984 f[p_, e_] := If[e == 1, -1, 0]; f[2, e_] := If[e == 1, 0, 2^(e-2)]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, May 09 2023 *)
%Y A361984 Partial sums give A309288.
%Y A361984 Cf. A361985, A361986.
%Y A361984 Cf. A092673.
%K A361984 sign,mult
%O A361984 1,8
%A A361984 _Seiichi Manyama_, Apr 02 2023