

A090669


Numbers n such that 7^n  2 is a prime.


24



1, 2, 4, 7, 8, 12, 15, 28, 31, 84, 98, 128, 238, 302, 859, 1508, 1586, 2091, 2796, 2888, 3924, 4815, 5636, 6596, 7090, 20176, 22176, 56386, 84050, 115515
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OFFSET

1,2


COMMENTS

No more terms through 50000.  Ryan Propper, Dec 07 2008


LINKS

Table of n, a(n) for n=1..30.


EXAMPLE

7^12  2 = 13841287199 a prime number.


MATHEMATICA

Do[ If[ PrimeQ[7^n  2], Print[n]], {n, 1, 2000}] (* Robert G. Wilson v, Dec 22 2003 *)


PROG

(PARI) is(n)=isprime(7^n  2) \\ Charles R Greathouse IV, Apr 28 2015


CROSSREFS

Cf. A236371, A217131, A191469, A090669, A096305, A217130, A217132, A152213.
Sequence in context: A216431 A233271 A088413 * A231428 A263660 A215822
Adjacent sequences: A090666 A090667 A090668 * A090670 A090671 A090672


KEYWORD

nonn


AUTHOR

Herman H. Rosenfeld (herm3(AT)pacbell.net), Dec 16 2003


EXTENSIONS

Corrected and extended by Robert G. Wilson v and Ray Chandler, Dec 22 2003
Three more terms from Ryan Propper, Dec 07 2008
a(28)a(30) from Robert Price, Jan 24 2014


STATUS

approved



