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A068582
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Let phi_m(x) = phi(phi(...(phi(x))...)) m times; sequence gives values of k such that phi_5(k) = tau(k).
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4
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1, 41, 47, 53, 59, 61, 67, 71, 73, 79, 85, 109, 115, 119, 123, 125, 127, 141, 143, 145, 155, 159, 161, 163, 166, 177, 178, 183, 185, 194, 201, 202, 203, 206, 209, 213, 214, 215, 217, 219, 226, 237, 247, 255, 259, 262, 278, 298, 301, 302, 314, 327, 328, 343
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OFFSET
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1,2
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COMMENTS
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Last term is a(340) = 24570.
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LINKS
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MATHEMATICA
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Select[Range[343], Nest[EulerPhi, #, 5] === DivisorSigma[0, #] &] (* Amiram Eldar, Jun 12 2022 *)
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CROSSREFS
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KEYWORD
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nonn,easy,fini,full
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AUTHOR
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STATUS
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approved
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