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 A378218 #8 Nov 22 2024 20:32:27
%S A378218 1,0,-1,-1,-1,-2,-1,-2,-1,-2,-1,-3,-1,-2,-1,-3,-1,-2,-1,-3,-1,-2,-1,
%T A378218 -4,-1,-2,-1,-3,-1,-2,-1,-4,-1,-2,-1,-3,-1,-2,-1,-4,-1,-2,-1,-3,-1,-2,
%U A378218 -1,-5,-1,-2,-1,-3,-1,-2,-1,-4,-1,-2,-1,-3,-1,-2,-1,-5,-1,-2,-1,-3,-1,-2,-1,-4,-1,-2,-1,-3,-1,-2,-1,-5
%N A378218 Dirichlet inverse of A345182.
%H A378218 Antti Karttunen, <a href="/A378218/b378218.txt">Table of n, a(n) for n = 1..65537</a>
%F A378218 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A345182(n/d) * a(d).
%F A378218 Apparently, abs(a(n+1)) = A359508(n).
%o A378218 (PARI)
%o A378218 memoA345182 = Map();
%o A378218 A345182(n) = if(n<=2, n%2, my(v); if(mapisdefined(memoA345182,n,&v), v, v = sumdiv(n,d,if(d<n,A345182(d),0)); mapput(memoA345182,n,v); (v)));
%o A378218 memoA378218 = Map();
%o A378218 A378218(n) = if(1==n,1,my(v); if(mapisdefined(memoA378218,n,&v), v, v = -sumdiv(n,d,if(d<n,A345182(n/d)*A378218(d),0)); mapput(memoA378218,n,v); (v)));
%Y A378218 Cf. A345182, A359508.
%K A378218 sign
%O A378218 1,6
%A A378218 _Antti Karttunen_, Nov 22 2024