A279183 - OEIS

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A279183

Numbers k such that phi(6k) = phi(6k-2), where phi is Euler's totient function A000010.

1, 2, 12, 152, 222, 362, 432, 992, 1517, 2532, 2567, 8472, 34732, 44092, 69312, 82752, 105852, 114392, 128672, 336992, 350082, 393132, 393552, 462747, 497712, 559872, 665817, 714502, 931432, 968952, 1126602, 1281867, 1389337, 1449992, 1638712, 1694292

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

Dov Jarden, Recurring Sequences, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 67.

MATHEMATICA

a = {}; Do[If[EulerPhi[6k] == EulerPhi[6 k - 2], AppendTo[a, k]], {k, 1000000}]; a (* Vincenzo Librandi, Dec 11 2016 *)

PROG

(Magma) [n: n in [1..2*10^6] | EulerPhi(6*n) eq EulerPhi(6*n-2)]; // Vincenzo Librandi, Dec 11 2016

(PARI) isok(k) = eulerphi(6*k) == eulerphi(6*k-2); \\ Michel Marcus, Dec 11 2016

CROSSREFS

A279011 is the union of A279183 and A279184. Cf. A000010.

Sequence in context: A374869 A340026 A279011 * A126777 A126345 A229558

Adjacent sequences: A279180 A279181 A279182 * A279184 A279185 A279186

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 10 2016

EXTENSIONS

More terms from Vincenzo Librandi, Dec 11 2016

STATUS

approved