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A293188
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Unitary pseudoperfect numbers: numbers that equal to the sum of a subset of their aliquot unitary divisors.
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15
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6, 30, 42, 60, 66, 78, 90, 102, 114, 138, 150, 174, 186, 210, 222, 246, 258, 282, 294, 318, 330, 354, 366, 390, 402, 420, 426, 438, 462, 474, 498, 510, 534, 546, 570, 582, 606, 618, 630, 642, 654, 660, 678, 690, 714, 726, 750, 762, 770, 780, 786, 798, 822
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OFFSET
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1,1
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COMMENTS
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The nonsquarefree terms are 60, 90, 150, 294, 420, 630, 660, 726, 750, 780, 840, ...
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LINKS
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EXAMPLE
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150 is in the sequence since its unitary aliquot divisors are 1, 2, 3, 6, 25, 50, 75 and 150 = 25 + 50 + 75.
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MATHEMATICA
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udiv[n_]:=Block[{d=Divisors[n]}, Select[d, GCD[#, n/#]==1&]]; a={}; n=0; While[Length[a]<100, n++; d=Most[udiv[n]]; c = SeriesCoefficient[ Series[ Product[1+x^d[[i]], {i, Length[d]} ], {x, 0, n}], n]; If[c>0, AppendTo[a, n]]]; a (* after T. D. Noe at A005835 *)
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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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