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 A378452 #7 Nov 29 2024 21:04:46
%S A378452 1,-1,-1,0,-1,0,-1,0,0,0,-1,1,-1,0,0,0,-1,1,-1,1,0,0,-1,0,0,0,0,1,-1,
%T A378452 2,-1,0,0,0,0,0,-1,0,0,0,-1,2,-1,1,1,0,-1,0,0,1,0,1,-1,0,0,0,0,0,-1,0,
%U A378452 -1,0,1,0,0,2,-1,1,0,2,-1,-1,-1,0,1,1,0,2,-1,0,0,0,-1,0,0,0,0,0,-1,0,0,1,0,0,0,0,-1,1,1,0
%N A378452 Dirichlet inverse of A007875, where A007875(n) = phi(2^omega(n)).
%C A378452 Inverse Möbius transform of A378453.
%H A378452 Antti Karttunen, <a href="/A378452/b378452.txt">Table of n, a(n) for n = 1..20000</a>
%F A378452 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A007875(n/d) * a(d).
%F A378452 a(n) = Sum_{d|n} A378453(d).
%o A378452 (PARI)
%o A378452 A007875(n) = eulerphi(2^omega(n));
%o A378452 memoA378452 = Map();
%o A378452 A378452(n) = if(1==n,1,my(v); if(mapisdefined(memoA378452,n,&v), v, v = -sumdiv(n,d,if(d<n,A007875(n/d)*A378452(d),0)); mapput(memoA378452,n,v); (v)));
%Y A378452 Cf. A007875, A378453 (Möbius transform).
%K A378452 sign
%O A378452 1,30
%A A378452 _Antti Karttunen_, Nov 29 2024