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A279011
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Numbers k such that phi(6k) is either phi(6k-2) or phi(6k+2), where phi is Euler's totient function A000010.
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2
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1, 2, 12, 152, 222, 268, 362, 432, 723, 992, 1517, 2532, 2567, 8472, 9718, 9858, 13498, 15738, 34732, 35898, 44092, 60363, 69312, 75168, 75973, 82752, 87208, 88888, 98198, 105852, 114392, 126848, 128672, 135368, 141093, 161268, 221223, 233788, 301513, 328358
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OFFSET
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1,2
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LINKS
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Dov Jarden, Recurring Sequences, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 67.
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MATHEMATICA
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Select[Range[10^6], Function[k, Or @@ Map[EulerPhi[6 k] == EulerPhi@ # &, 6 k + {-2, 2}]]] (* Michael De Vlieger, Dec 12 2016 *)
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PROG
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(Magma) [n: n in [1..1000000] | not (EulerPhi(6*n) eq EulerPhi(6*n-2)) eq (EulerPhi(6*n) eq EulerPhi(6*n+2))]; // Vincenzo Librandi, Dec 12 2016
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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