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A066685 Numbers n such that p(n) is congruent to EulerPhi(n) mod n, where p(n) denotes the n-th prime. 0
1, 2, 3, 789, 40087, 238717, 251737, 7847315, 69673727, 2283427137, 2664260621 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(12) > 10^12. - Donovan Johnson, Mar 14 2010

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

p(1) = 2 is congruent to 0 mod 1, and EulerPhi(1) = 1 is congruent to 0 mod 1, so 1 is a term of the sequence.

p(3) = 5 is congruent to 2 mod 3, and EulerPhi(3) = 2 is congruent to 2 mod 3, so 3 is a term of the sequence.

MATHEMATICA

Select[ Range[ 1, 10^6 ], Mod[ EulerPhi[ # ], # ] == Mod[ Prime[ # ], # ] & ]

PROG

(PARI) print1(n=1); forprime(p=3, 1e9, if(p%n++==eulerphi(n), print1(", "n))) \\ Charles R Greathouse IV, Mar 04 2017

CROSSREFS

Sequence in context: A226148 A108332 A256115 * A076155 A136611 A004898

Adjacent sequences:  A066682 A066683 A066684 * A066686 A066687 A066688

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Jan 11 2002

EXTENSIONS

Examples revised by N. J. A. Sloane, Jan 31 2010

a(8)-a(11) from Donovan Johnson, Mar 14 2010

STATUS

approved

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Last modified April 13 14:11 EDT 2021. Contains 342936 sequences. (Running on oeis4.)