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A243282
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Partial sums of the characteristic function for A070003.
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5
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0, 0, 0, 1, 1, 1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16
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OFFSET
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1,8
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COMMENTS
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a(n) tells how many natural numbers <= n there are which are divisible by the square of their largest prime divisor. (This definition excludes 1 as it has no prime divisors.)
For all n, a(A070003(n)) = n, thus this sequence works also as an inverse function for the injection A070003.
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LINKS
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FORMULA
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EXAMPLE
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A070003(402) = 10000, thus a(10000) = 402.
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MATHEMATICA
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Accumulate[Join[{0}, Table[If[Divisible[n, Last[Select[Divisors[n], PrimeQ]]^2], 1, 0], {n, 2, 90}]]] (* Harvey P. Dale, Sep 05 2018 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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