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A286322
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Totient highly abundant numbers that are composite.
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1
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4, 9, 221, 289, 697, 1819, 2329, 4369, 4913, 6439, 18769, 21331, 35209, 66049, 128881, 184783, 197143, 258121, 281929, 516961, 739903, 971203, 1762249, 1942663, 2070721, 2898703, 2952673, 3820819, 4142881, 5550943, 5869681, 8288641, 16230481, 16773619
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OFFSET
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1,1
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COMMENTS
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Of the 65 terms below 10^9, only 2 have more than 2 prime factors: a(9) = 17^3 and a(36) = 257^3, and 11 are prime powers: a(1) = 2^2, a(2) = 3^2, a(4) = 17^2, a(9) = 17^3, a(11) = 137^2, a(14) = 257^2, a(15) = 359^2, a(20) = 719^2, a(25) = 1439^2, a(32) = 2879^2, and a(36) = 257^3.
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LINKS
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MATHEMATICA
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sumTot[n_] := Plus @@ FixedPointList[ EulerPhi@ # &, n] - 1; a={}; smax=0; For[k=1, k<300000, k++; s=sumTot[k]; If[s>smax, smax=s; If[!PrimeQ[k], a=AppendTo[a, k]]]]; a
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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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