A067796 Numbers k such that phi(k) + phi(k+1) = k.

14, 20, 44, 140, 254, 272, 284, 344, 464, 764, 1224, 1424, 2064, 3200, 3824, 11648, 21584, 25520, 27644, 38840, 116544, 235584, 603584, 632400, 1677024, 1935344, 2049984, 3763184, 18460224, 74649584, 82448384, 86648000, 97507584, 363939824, 646139264, 4294967294

Offset: 1

Author

Benoit Cloitre, Feb 07 2002

Keywords

• nonn

Crossrefs

Cf. A000010, A092404.

Programs

Mathematica

Select[Range[10^6], EulerPhi[#] + EulerPhi[# + 1] == # &] (* Amiram Eldar, Apr 23 2022 *)

Extensions

a(22)-a(33) from Donovan Johnson, Mar 24 2011

a(34)-a(36) from Amiram Eldar, Apr 23 2022