

A066685


Numbers n such that p(n) is congruent to EulerPhi(n) mod n, where p(n) denotes the nth prime.


0



1, 2, 3, 789, 40087, 238717, 251737, 7847315, 69673727, 2283427137, 2664260621
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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



