A067797 Numbers k such that phi(k) + phi(k+1) = k+2.

4, 6, 8, 50, 74, 110, 170, 174, 890, 902, 1310, 1434, 1826, 2714, 4190, 5030, 6494, 8234, 8474, 10142, 14390, 31670, 32394, 40514, 89990, 95174, 101834, 102554, 135374, 151754, 173942, 206054, 248394, 259694, 288266, 330614, 516242, 650654, 780554, 913994, 941714

Offset: 1

Author

Benoit Cloitre, Feb 07 2002

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..72

Crossrefs

Cf. A000010, A092404.

Programs

Mathematica

Select[Range[10^6],EulerPhi[#]+EulerPhi[#+1]==#+2&] (* Harvey P. Dale, Apr 04 2019 *)

PARI

isok(n) = eulerphi(n) + eulerphi(n+1) == n+2; \\ Michel Marcus, Nov 23 2013

Extensions

More terms from Michel Marcus, Nov 23 2013