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A226117
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Numbers n such that phi(sigma(tau(n))) = tau(sigma(phi(n))).
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3
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1, 3, 4, 5, 14, 17, 20, 21, 22, 26, 51, 63, 65, 66, 72, 76, 80, 84, 90, 100, 106, 112, 132, 135, 150, 152, 165, 182, 190, 196, 221, 222, 232, 246, 255, 290, 291, 292, 294, 320, 326, 375, 386, 396, 424, 450, 460, 489, 530, 561, 567, 585, 588, 600, 606, 608, 615
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OFFSET
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1,2
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LINKS
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EXAMPLE
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For n=23529 we have:
phi(23529)=13200 -> sigma(13200)=46128 -> tau(46128)=30.
tau(23529)=16 -> sigma(16)=31 -> phi(31)=30.
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MAPLE
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with(numtheory); A226117:=proc(q) local n;
for n from 1 to q do
if phi(sigma(tau(n)))=tau(sigma(phi(n))) then print(n);
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MATHEMATICA
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Select[Range[700], EulerPhi[DivisorSigma[1, DivisorSigma[0, #]]] == DivisorSigma[ 0, DivisorSigma[ 1, EulerPhi[ #]]]&] (* Harvey P. Dale, Dec 12 2021 *)
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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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