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A348121
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Numbers having more nonunitary than unitary prime divisors.
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3
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4, 8, 9, 16, 25, 27, 32, 36, 49, 64, 72, 81, 100, 108, 121, 125, 128, 144, 169, 180, 196, 200, 216, 225, 243, 252, 256, 288, 289, 300, 324, 343, 360, 361, 392, 396, 400, 432, 441, 450, 468, 484, 500, 504, 512, 529, 540, 576, 588, 600, 612, 625, 648, 675, 676, 684
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OFFSET
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1,1
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COMMENTS
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First differs from A080366 at n = 20.
The first 19 terms are also the first 19 powerful numbers (A001694) above 1. a(20) = 180 is the least nonpowerful term.
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LINKS
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EXAMPLE
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4 = 2^2 is a term since it has 1 nonunitary prime divisor, 2, and no unitary prime divisors.
180 = 2^2 * 3^2 * 5 is a term since it has 2 nonunitary prime divisors, 2 and 3, and one unitary prime divisor, 5.
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MATHEMATICA
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q[n_] := 2*Count[(e = FactorInteger[n][[;; , 2]]), 1] < Length[e]; Select[Range[700], q]
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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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