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A070418
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Numbers k such that k and phi(k) have the same number of divisors.
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4
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1, 3, 14, 15, 22, 28, 44, 46, 50, 56, 68, 70, 78, 88, 92, 94, 110, 112, 118, 166, 174, 176, 184, 188, 198, 214, 224, 228, 230, 234, 236, 255, 260, 294, 306, 318, 332, 334, 342, 352, 358, 368, 376, 414, 428, 448, 454, 462, 470, 472, 492, 500, 526, 550, 580, 590
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OFFSET
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1,2
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COMMENTS
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This is an infinite sequence; for example, 2^(m-1)*5^m is in the sequence for all m >= 2. See Bellaouar et al. 2023. - Allen Stenger, Feb 16 2024
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LINKS
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MATHEMATICA
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Select[Range[600], DivisorSigma[0, #]==DivisorSigma[0, EulerPhi[#]]&] (* Harvey P. Dale, Sep 04 2015 *)
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PROG
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(PARI) for(n=1, 900, if(numdiv(n)==numdiv(eulerphi(n)), print1(n, ", ")))
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CROSSREFS
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KEYWORD
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easy,nonn,changed
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AUTHOR
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STATUS
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approved
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