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sum[k=1 to n] mu(k)+sqf(k): mu(k) is Moebius function; sqf(k)=1 if k is squarefree, sqf(k)=-1 otherwise.
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%I #8 Jun 02 2022 20:39:03

%S 2,2,2,1,1,3,3,2,1,3,3,2,2,4,6,5,5,4,4,3,5,7,7,6,5,7,6,5,5,5,5,4,6,8,

%T 10,9,9,11,13,12,12,12,12,11,10,12,12,11,10,9,11,10,10,9,11,10,12,14,

%U 14,13,13,15,14,13,15,15,15,14,16,16,16,15,15,17,16,15,17,17,17,16,15

%N sum[k=1 to n] mu(k)+sqf(k): mu(k) is Moebius function; sqf(k)=1 if k is squarefree, sqf(k)=-1 otherwise.

%t Accumulate[Table[MoebiusMu[n]+If[SquareFreeQ[n],1,-1],{n,100}]] (* _Harvey P. Dale_, Jun 02 2022 *)

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Oct 19 2002