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 A160764 a(n) = n-th squarefree number minus round(n*zeta(2)). 3
 -1, -1, -2, -2, -2, -3, -2, -2, -2, -2, -3, -3, -2, -2, -3, -3, -2, -1, -1, -2, -2, -2, -3, -2, -3, -4, -3, -4, -5, -3, -4, -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -2, -2, -2, -3, -3, -3, -2, -3, -3, -2, -3, -2, -3, -3, -3, -3, -2, -3, -4, -3, -1, -2, -2, -2, -3, -3, -3, -4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Race between the n-th squarefree number and round(n*zeta(2)). LINKS Daniel Forgues, Table of n, a(n) for n=1..60794 FORMULA Since zeta(2) = Sum[{i, 1, inf}, {1/(i^2)}] = (pi^2)/6, we get: a(n) = A005117(n) - n * Sum[{i, 1, inf}, {1/(i^2)}] = O(sqrt(n)) a(n) = A005117(n) - n * (pi^2)/6 = O(sqrt(n)) CROSSREFS Cf. A005117 Squarefree numbers. Cf. A013929 Not squarefree numbers. Cf. A013928 Number of squarefree numbers < n. Cf. A158819 Number of squarefree numbers <= n minus round(n/zeta(2)). Sequence in context: A130192 A175064 A104564 * A156384 A064656 A056608 Adjacent sequences:  A160761 A160762 A160763 * A160765 A160766 A160767 KEYWORD sign AUTHOR Daniel Forgues, May 26 2009 STATUS approved

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