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 A369453 #10 Jan 27 2024 10:32:25
%S A369453 1,-1,-1,-1,-1,0,-1,1,-1,0,-1,2,-1,0,0,0,-1,2,-1,2,0,0,-1,0,-1,0,1,2,
%T A369453 -1,2,-1,0,0,0,0,1,-1,0,0,0,-1,2,-1,2,2,0,-1,-1,-1,2,0,2,-1,0,0,0,0,0,
%U A369453 -1,0,-1,0,2,0,0,2,-1,2,0,2,-1,-3,-1,0,2,2,0,2,-1,-1,0,0,-1,0,0,0,0,0,-1,0,0,2,0,0,0,0,-1,2,2
%N A369453 Dirichlet inverse of A038548, where A038548 is the number of divisors of n that are at most sqrt(n).
%H A369453 Antti Karttunen, <a href="/A369453/b369453.txt">Table of n, a(n) for n = 1..65537</a>
%F A369453 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A038548(n/d) * a(d).
%F A369453 Dirichlet g.f.: 2/(zeta(s)^2 + zeta(2*s)).
%o A369453 (PARI)
%o A369453 A038548(n) = if( n<1, 0, sumdiv(n, d, d*d <= n))
%o A369453 memoA369453 = Map();
%o A369453 A369453(n) = if(1==n,1,my(v); if(mapisdefined(memoA369453,n,&v), v, v = -sumdiv(n,d,if(d<n,A038548(n/d)*A369453(d),0)); mapput(memoA369453,n,v); (v)));
%Y A369453 Cf. A038548.
%Y A369453 Cf. also A359763, A369454.
%K A369453 sign
%O A369453 1,12
%A A369453 _Antti Karttunen_, Jan 27 2024