A279011 Numbers k such that phi(6k) is either phi(6k-2) or phi(6k+2), where phi is Euler's totient function A000010.

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

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..1554

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

Mathematica

Select[Range[10^6], Function[k, Or @@ Map[EulerPhi[6 k] == EulerPhi@ # &, 6 k + {-2, 2}]]] (* Michael De Vlieger, Dec 12 2016 *)

Prog

(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

Crossrefs

Cf. A000010.

Union of A279183 and A279184.

Sequence in context: A375233 A374869 A340026 * A279183 A126777 A126345

Adjacent sequences: A279008 A279009 A279010 * A279012 A279013 A279014

Keyword

nonn,changed

Author

N. J. A. Sloane, Dec 10 2016

Extensions

More terms from Vincenzo Librandi, Dec 12 2016

Status

approved