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 A353455 #11 Apr 21 2022 11:24:46
%S A353455 1,1,-1,1,1,-1,-1,1,0,1,1,-1,-1,-1,1,1,1,0,-1,1,1,1,1,-1,0,-1,0,-1,-1,
%T A353455 1,1,1,1,1,-1,0,-1,-1,1,1,1,1,-1,1,2,1,1,-1,0,0,1,-1,-1,0,-3,-1,1,-1,
%U A353455 1,1,-1,1,0,1,-1,1,1,1,1,-1,-1,0,1,-1,0,-1,1,1,-1,1,0,1,1,1,-3,-1,1,1,-1,2,-3,1,1,1,-1
%N A353455 a(n) = A353454(A064989(n)).
%H A353455 Antti Karttunen, <a href="/A353455/b353455.txt">Table of n, a(n) for n = 1..10000</a>
%H A353455 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%F A353455 For all n >= 1, a(A000040(n)) = ((-1)^(n-1)).
%o A353455 (PARI)
%o A353455 A000265(n) = (n>>valuation(n,2));
%o A353455 A064989(n) = { my(f=factor(A000265(n))); for(i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f); };
%o A353455 memoA353454 = Map();
%o A353455 A353454(n) = if(1==n,1,my(v); if(mapisdefined(memoA353454,n,&v), v, v = -sumdiv(n,d,if(d<n,A353454(A064989(n))*A353454(d),0)); mapput(memoA353454,n,v); (v)));
%o A353455 A353455(n) = A353454(A064989(n));
%Y A353455 Cf. A000040, A064989, A353454.
%Y A353455 Cf. also A353458.
%K A353455 sign
%O A353455 1,45
%A A353455 _Antti Karttunen_, Apr 21 2022