A116045 n+phi(n)+phi(phi(n)) is a prime.

1, 4, 5, 9, 13, 17, 19, 21, 25, 33, 35, 39, 41, 43, 49, 61, 75, 79, 85, 87, 95, 101, 121, 133, 137, 141, 153, 155, 159, 163, 165, 169, 177, 181, 193, 199, 201, 203, 207, 213, 215, 231, 233, 245, 251, 257, 259, 265, 267, 271, 277, 291, 299, 307, 309, 337, 339

Offset

1,2

Links

Table of n, a(n) for n=1..57.

Example

13+phi(13)+phi(phi(13)) = 29.

Mathematica

epQ[n_]:=Module[{ep=EulerPhi[n]}, PrimeQ[n+ep+EulerPhi[ep]]]
Select[Range[400], epQ]  (* Harvey P. Dale, Mar 06 2011 *)

Crossrefs

Cf. A068080.

Sequence in context: A363267 A328223 A363282 * A096818 A282467 A318980

Adjacent sequences: A116042 A116043 A116044 * A116046 A116047 A116048

Keyword

nonn

Author

Giovanni Resta, Feb 13 2006

Status

approved