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 A378997 #6 Dec 16 2024 14:28:14
%S A378997 1,-2,-3,-2,-5,6,-7,2,-3,10,-11,6,-13,14,15,6,-17,6,-19,10,21,22,-23,
%T A378997 -6,-5,26,6,14,-29,-30,-31,2,33,34,35,6,-37,38,39,-10,-41,-42,-43,22,
%U A378997 15,46,-47,-18,-7,10,51,26,-53,-12,55,-14,57,58,-59,-30,-61,62,21,-10,65,-66,-67,34,69,-70,-71,-6,-73,74,15
%N A378997 Dirichlet inverse of A057723.
%H A378997 Antti Karttunen, <a href="/A378997/b378997.txt">Table of n, a(n) for n = 1..20000</a>
%F A378997 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A057723(n/d) * a(d).
%o A378997 (PARI)
%o A378997 A057723(n) = { my(f=factor(n)~); prod(i=1, #f, sigma(f[1, i]^f[2,i])-1); };
%o A378997 memoA378997 = Map();
%o A378997 A378997(n) = if(1==n,1,my(v); if(mapisdefined(memoA378997,n,&v), v, v = -sumdiv(n,d,if(d<n,A057723(n/d)*A378997(d),0)); mapput(memoA378997,n,v); (v)));
%Y A378997 Cf. A057723.
%K A378997 sign,mult
%O A378997 1,2
%A A378997 _Antti Karttunen_, Dec 16 2024