cp's OEIS Frontend

A087802 a(n) = Sum_{d|n, d nonprime} mu(d), where mu = A008683.

%I A087802 #16 Feb 14 2022 21:28:35
%S A087802 1,1,1,1,1,2,1,1,1,2,1,2,1,2,2,1,1,2,1,2,2,2,1,2,1,2,1,2,1,3,1,1,2,2,
%T A087802 2,2,1,2,2,2,1,3,1,2,2,2,1,2,1,2,2,2,1,2,2,2,2,2,1,3,1,2,2,1,2,3,1,2,
%U A087802 2,3,1,2,1,2,2,2,2,3,1,2,1,2,1,3,2,2,2,2,1,3,2,2,2,2,2,2,1,2,2,2,1,3
%N A087802 a(n) = Sum_{d|n, d nonprime} mu(d), where mu = A008683.
%C A087802 A064372 and this sequence first differ at term 64: A064372(64)=2 and a(64)=1. - _Rick L. Shepherd_, Mar 07 2004
%H A087802 G. C. Greubel, <a href="/A087802/b087802.txt">Table of n, a(n) for n = 1..1000</a>
%F A087802 a(n) = if n=1 then 1, else A001221(n). - _Vladeta Jovovic_, Oct 17 2003
%e A087802 Divisors of n=42: {1,2,3,6,7,14,21,42}, a(42) = mu(1) + mu(6) + mu(14) + mu(21) + mu(42) = 1+1+1+1-1 = 3.
%t A087802 Table[Total[MoebiusMu[#]&/@Select[Divisors[n],!PrimeQ[#]&]],{n,120}] (* _Harvey P. Dale_, Oct 14 2014 *)
%o A087802 (PARI) A087802(n) = sumdiv(n,d,if(!isprime(d),moebius(d)))
%Y A087802 Cf. A001221, A008683 (mu), A023890, A033273. Different from A079553.
%K A087802 nonn
%O A087802 1,6
%A A087802 _Reinhard Zumkeller_, Oct 11 2003