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 A066779 Sum of squarefree numbers <=n. 5
 1, 3, 6, 6, 11, 17, 24, 24, 24, 34, 45, 45, 58, 72, 87, 87, 104, 104, 123, 123, 144, 166, 189, 189, 189, 215, 215, 215, 244, 274, 305, 305, 338, 372, 407, 407, 444, 482, 521, 521, 562, 604, 647, 647, 647, 693, 740, 740, 740, 740, 791, 791, 844, 844, 899, 899 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harry J. Smith, Table of n, a(n) for n = 1..1000 FORMULA a(n)=sum(i=1, n, mu(i)^2*i). a(n) = SUM(k*A008966(k): 1 <= k <= n). [From Reinhard Zumkeller, Jul 05 2010] a(n) = sum(d=1, sqrt(n), mu(d)*d^2*floor(n/d^2)*floor(n/d^2+1))/2. - Charles R Greathouse IV, Apr 26 2012 PROG (PARI) { s=0; for (n=1, 1000, write("b066779.txt", n, " ", s+=moebius(n)^2*n) ) } [From Harry J. Smith, Mar 24 2010] (PARI) a(n)=sum(d=1, sqrtint(n), moebius(d)*d^2*binomial(n\d^2+1, 2)) \\ Charles R Greathouse IV, Apr 26 2012 CROSSREFS Cf. A013928, A034387, A179213, A179215. Sequence in context: A210692 A158662 A119980 * A132384 A201155 A200534 Adjacent sequences:  A066776 A066777 A066778 * A066780 A066781 A066782 KEYWORD nonn,easy AUTHOR Benoit Cloitre, Jan 18 2002 STATUS approved

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