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A083730
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Greatest prime^2 factor of n, or a(n)=1 for squarefree n.
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2
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1, 1, 1, 4, 1, 1, 1, 4, 9, 1, 1, 4, 1, 1, 1, 4, 1, 9, 1, 4, 1, 1, 1, 4, 25, 1, 9, 4, 1, 1, 1, 4, 1, 1, 1, 9, 1, 1, 1, 4, 1, 1, 1, 4, 9, 1, 1, 4, 49, 25, 1, 4, 1, 9, 1, 4, 1, 1, 1, 4, 1, 1, 9, 4, 1, 1, 1, 4, 1, 1, 1, 9, 1, 1, 25, 4, 1, 1, 1, 4, 9, 1, 1, 4, 1, 1, 1, 4, 1, 9, 1, 4, 1, 1, 1, 4, 1, 49, 9
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OFFSET
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1,4
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COMMENTS
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Not multiplicative, for example a(4)*a(9) <> a(36). - R. J. Mathar, Oct 31 2011
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := If[(pos = Position[(f = FactorInteger[n])[[;; , 2]], _?(# >= 2 &)]) == {}, 1, f[[pos[[-1, 1]], 1]]^2]; Array[a, 100] (* Amiram Eldar, Nov 14 2020 *)
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PROG
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(PARI) a(n)=my(f=factor(n)); forstep(i=#f~, 1, -1, if(f[i, 2]>1, return(f[i, 1]^2))); 1 \\ Charles R Greathouse IV, Jul 23 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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