

A109889


Numbers n such that 3^n  phi(n) is prime.


0



1, 4, 5, 6, 20, 22, 25, 46, 47, 214, 822, 985, 3273, 3590, 4658, 4768, 17250, 38697
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OFFSET

1,2


COMMENTS

Terms less than 1000 correspond to certified primes. Next term is greater than 10000.
a(19) > 10^5. [From Donovan Johnson, Feb 06 2010]


LINKS

Table of n, a(n) for n=1..18.


MATHEMATICA

Do[If[PrimeQ[3^n  EulerPhi[n]], Print[n]], {n, 1, 10^4}]


CROSSREFS

Sequence in context: A010753 A221174 A047195 * A103518 A103313 A036492
Adjacent sequences: A109886 A109887 A109888 * A109890 A109891 A109892


KEYWORD

hard,nonn


AUTHOR

Ryan Propper, Aug 31 2005


EXTENSIONS

a(17)a(18) from Donovan Johnson, Feb 06 2010


STATUS

approved



