A279184 Numbers k such that phi(6k) = phi(6k+2), where phi is Euler's totient function A000010.

268, 723, 9718, 9858, 13498, 15738, 35898, 60363, 75168, 75973, 87208, 88888, 98198, 126848, 135368, 141093, 161268, 221223, 233788, 301513, 328358, 330633, 419148, 507648, 527928, 543468, 551238, 556418, 586018, 725958, 772508, 964588, 985728

Offset: 1

Author

N. J. A. Sloane, Dec 10 2016

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..794
• Dov Jarden, Recurring Sequences, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 67.

Crossrefs

Cf. A000010.

A279011 is the union of A279183 and A279184.

Programs

Magma

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

Maple

select( k -> numtheory:-phi(6*k)=numtheory:-phi(6*k+2), [$1..10^6]); # Robert Israel, Dec 11 2016

Mathematica

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

PARI

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

Extensions

a(8)-a(33) from Robert Israel, Dec 11 2016