

A070549


a(n) = Card(k 0<k<=n such that mu(k)=1).


3



0, 1, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 14, 15, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 20, 21, 22, 22, 22, 23, 24, 24, 25, 25, 25, 25, 25, 26
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OFFSET

1,3


COMMENTS

mu(k)=1 if k is the product of an odd number of distinct primes. See A057627 for mu(k)=0.


LINKS



MAPLE

ListTools:PartialSums([seq(min(numtheory:mobius(n), 0), n=1..100)]); # Robert Israel, Jan 08 2018


MATHEMATICA

a[n_]:=Sum[Boole[MoebiusMu[k]==1], {k, n}]; Array[a, 78] (* Stefano Spezia, Jan 30 2023 *)


PROG

(PARI) for(n=1, 150, print1(sum(i=1, n, if(moebius(i)+1, 0, 1)), ", "))


CROSSREFS



KEYWORD

easy,nonn


AUTHOR



STATUS

approved



