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 A053462 Number of positive squarefree integers less than 10^n. 9
 0, 6, 61, 608, 6083, 60794, 607926, 6079291, 60792694, 607927124, 6079270942, 60792710280, 607927102274, 6079271018294, 60792710185947, 607927101854103, 6079271018540405, 60792710185403794, 607927101854022750 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n)/10^n = 6/Pi^2*(1+o(1)), cf. A059956. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 0..20 G. P. Michon, On the number of squarefree integers not exceeding N. - Gerard P. Michon, Apr 30 2009 EXAMPLE There are 608 squarefree integers smaller than 1000. MATHEMATICA a[n_] := Module[{t=10^n-1}, Sum[MoebiusMu[k]Floor[t/k^2], {k, 1, Sqrt[t]}]] PROG (PARI) a(n)=sum(d=1, sqrtint(n=10^n-1), n\d^2*moebius(d)) \\ Charles R Greathouse IV, Nov 14 2012 (PARI) a(n)=my(s); forsquarefree(d=1, sqrtint(n=10^n-1), s += n\d[1]^2 * moebius(d)); s \\ Charles R Greathouse IV, Jan 08 2018 CROSSREFS Cf. A059956, A063035. Apart from initial term, same as A071172. Binary counterpart is A143658. - Gerard P. Michon, Apr 30 2009 Sequence in context: A069618 A155458 A152281 * A160751 A236670 A142970 Adjacent sequences:  A053459 A053460 A053461 * A053463 A053464 A053465 KEYWORD nonn AUTHOR Harvey P. Dale, Aug 01 2001 EXTENSIONS More terms from Dean Hickerson and Vladeta Jovovic, Aug 06, 2001 One more term from Jud McCranie, Sep 01 2005 a(0)=0 and a(14)-a(17) from Gerard P. Michon, Apr 30 2009 a(18) from Charles R Greathouse IV, Jan 08 2018 STATUS approved

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Last modified October 14 07:19 EDT 2019. Contains 327995 sequences. (Running on oeis4.)