A117296 - OEIS

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A117296

Numbers n for which phi(n) is a palindrome.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 23, 24, 30, 46, 67, 69, 89, 92, 115, 134, 138, 178, 184, 223, 230, 233, 263, 276, 283, 289, 293, 295, 301, 321, 381, 387, 411, 428, 441, 446, 466, 472, 508, 526, 535, 548, 566, 578, 586, 590

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..2000

EXAMPLE

69 is in the sequence because phi(69)=44 which is a palindrome.

MATHEMATICA

Select[Range[600], FromDigits[Reverse[IntegerDigits[EulerPhi[ # ]]]]==EulerPhi[ # ] &] (* Stefan Steinerberger, Apr 24 2006 *)

Select[Range[600], PalindromeQ[EulerPhi[#]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 21 2020 *)

CROSSREFS

Cf. A002113.