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 A378990 #9 Dec 15 2024 09:30:31
%S A378990 1,-1,-2,0,-2,2,-3,0,2,2,-3,0,-3,3,4,0,-2,-2,-3,0,9,3,-4,0,1,3,-4,0,
%T A378990 -4,-4,-5,0,10,2,9,0,-3,3,8,0,-3,-9,-4,0,-4,4,-5,0,6,-1,4,0,-4,4,7,0,
%U A378990 8,4,-5,0,-5,5,-18,0,10,-10,-3,0,13,-9,-4,0,-3,3,0,0,14,-8,-5,0,9,3,-4,0,4,4,11,0,-4,4,13,0,15
%N A378990 Dirichlet inverse of the binary weight of n (A000120).
%H A378990 Antti Karttunen, <a href="/A378990/b378990.txt">Table of n, a(n) for n = 1..65537</a>
%H A378990 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>
%F A378990 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A000120(n/d) * a(d).
%F A378990 a(n) = Sum_{d|n} A008683(d)*A378989(n/d).
%o A378990 (PARI)
%o A378990 memoA378990 = Map();
%o A378990 A378990(n) = if(1==n,1,my(v); if(mapisdefined(memoA378990,n,&v), v, v = -sumdiv(n,d,if(d<n,hammingweight(n/d)*A378990(d),0)); mapput(memoA378990,n,v); (v)));
%Y A378990 Dirichlet inverse of A000120.
%Y A378990 Möbius transform of A378989.
%Y A378990 Cf. A008683, A378991.
%K A378990 sign
%O A378990 1,3
%A A378990 _Antti Karttunen_, Dec 15 2024