cp's OEIS Frontend

A355694 Dirichlet inverse of A277791, denominator of sum of reciprocals of proper divisors of n.

%I A355694 #9 Jul 18 2022 16:39:24
%S A355694 1,-1,-1,-1,-1,-4,-1,-1,-2,-8,-1,9,-1,-12,-13,-1,-1,6,-1,1,-19,-20,-1,
%T A355694 -10,-4,-24,-4,1,-1,26,-1,-1,-31,-32,-33,27,-1,-36,-37,10,-1,34,-1,1,
%U A355694 -12,-44,-1,35,-6,2,-49,1,-1,-14,-53,62,-55,-56,-1,87,-1,-60,-18,-1,-63,110,-1,1,-67,42,-1,-57,-1,-72,12
%N A355694 Dirichlet inverse of A277791, denominator of sum of reciprocals of proper divisors of n.
%H A355694 Antti Karttunen, <a href="/A355694/b355694.txt">Table of n, a(n) for n = 1..12000</a>
%H A355694 Antti Karttunen, <a href="/A355694/a355694.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%F A355694 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A277791(n/d) * a(d).
%o A355694 (PARI)
%o A355694 A277791(n) = denominator((sigma(n)-1)/n); \\ From A277791
%o A355694 memoA355694 = Map();
%o A355694 A355694(n) = if(1==n,1,my(v); if(mapisdefined(memoA355694,n,&v), v, v = -sumdiv(n,d,if(d<n,A277791(n/d)*A355694(d),0)); mapput(memoA355694,n,v); (v)));
%Y A355694 Cf. A277791.
%K A355694 sign
%O A355694 1,6
%A A355694 _Antti Karttunen_, Jul 18 2022