

A128455


Numbers n such that 9^n  2 is a prime.


13



1, 2, 3, 11, 45, 51, 260, 324, 390, 393, 1112, 3092, 4445, 10373, 15861, 18528, 97715, 112961
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OFFSET

1,2


COMMENTS

a(19) > 2*10^5.  Robert Price, Aug 18 2014


LINKS

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


MATHEMATICA

Do[ f = 9^n  2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 1000} ]


CROSSREFS

Cf. A084714 = smallest prime of the form (2n1)^k  2, or 0 if no such number exists. Cf. A128472 = smallest prime of the form (2n1)^k  2 for k>(2n1), or 0 if no such number exists. Cf. A014224, A109080, A090669, A128457, A128458, A128459, A128460, A128461.
Sequence in context: A051093 A107327 A162101 * A260159 A287060 A041345
Adjacent sequences: A128452 A128453 A128454 * A128456 A128457 A128458


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Mar 14 2007


EXTENSIONS

1112 from Stefan Steinerberger, May 05 2007
More terms from Ryan Propper, Jan 12 2008
a(15)a(18) from Robert Price, Aug 18 2014


STATUS

approved



