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 A369454 #6 Jan 27 2024 10:32:33
%S A369454 1,-1,-1,0,-1,1,-1,0,-1,1,-1,0,-1,1,0,0,-1,1,-1,0,0,1,-1,0,-1,1,1,0,
%T A369454 -1,0,-1,0,0,1,0,0,-1,1,0,0,-1,0,-1,0,2,1,-1,0,-1,1,0,0,-1,-1,0,0,0,1,
%U A369454 -1,0,-1,1,2,0,0,0,-1,0,0,0,-1,0,-1,1,2,0,0,0,-1,0,0,1,-1,0,0,1,0,0,-1,-2,0,0,0,1,0,0,-1,1,2,0
%N A369454 Dirichlet inverse of A369257, where A369257 is the number of divisors of n that are odd numbers with an even number of prime factors with multiplicity.
%H A369454 Antti Karttunen, <a href="/A369454/b369454.txt">Table of n, a(n) for n = 1..65537</a>
%F A369454 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A369257(n/d) * a(d).
%o A369454 (PARI)
%o A369454 A353557(n) = ((n%2)&&(!(bigomega(n)%2)));
%o A369454 A369257(n) = sumdiv(n,d,A353557(d));
%o A369454 memoA369454 = Map();
%o A369454 A369454(n) = if(1==n,1,my(v); if(mapisdefined(memoA369454,n,&v), v, v = -sumdiv(n,d,if(d<n,A369257(n/d)*A369454(d),0)); mapput(memoA369454,n,v); (v)));
%Y A369454 Cf. A353557, A369257.
%Y A369454 Cf. also A358777, A369454.
%K A369454 sign
%O A369454 1,45
%A A369454 _Antti Karttunen_, Jan 27 2024