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A071172
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Number of squarefree integers <= 10^n.
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18
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1, 7, 61, 608, 6083, 60794, 607926, 6079291, 60792694, 607927124, 6079270942, 60792710280, 607927102274, 6079271018294, 60792710185947, 607927101854103, 6079271018540405, 60792710185403794
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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MATHEMATICA
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f[n_] := Sum[ MoebiusMu[i]Floor[n/i^2], {i, Sqrt@ n}]; Table[ f[10^n], {n, 0, 14}] (* Robert G. Wilson v, Aug 04 2012 *)
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PROG
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(PARI) a(n)=my(s); forsquarefree(d=1, sqrtint(n=10^n), s += n\d[1]^2 * moebius(d)); s \\ Charles R Greathouse IV, Jan 08 2018
(Python)
from math import isqrt
from sympy import mobius
def A071172(n): return sum(mobius(k)*(10**n//k**2) for k in range(1, isqrt(10**n)+1)) # Chai Wah Wu, May 10 2024
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CROSSREFS
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Apart from initial term, same as A053462.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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