

A128026


Numbers n such that (10^n  3^n)/7 is prime.


29




OFFSET

1,1


COMMENTS

All terms are primes.
No other terms < 100000.


LINKS

Table of n, a(n) for n=1..7.


MATHEMATICA

k=7; Select[ Prime[ Range[1, 200] ], PrimeQ[ ((k+3)^#  3^#)/k ]& ]


PROG

(PARI) forprime(p=2, 1e4, if(ispseudoprime((10^p3^p)/7), print1(p", "))) \\ Charles R Greathouse IV, Jun 05 2011


CROSSREFS

Cf. A028491 = numbers n such that (3^n  1)/2 is prime.
Cf. A057468 = numbers n such that 3^n  2^n is prime.
Cf. A059801 = numbers n such that 4^n  3^n is prime.
Cf. A121877 = numbers n such that (5^n  3^n)/2 is a prime.
Cf. A128024, A128025, A128027, A128028, A128029, A128030, A128031, A128032.
Sequence in context: A271387 A089213 A029499 * A041443 A057775 A215321
Adjacent sequences: A128023 A128024 A128025 * A128027 A128028 A128029


KEYWORD

hard,nonn


AUTHOR

Alexander Adamchuk, Feb 11 2007


EXTENSIONS

a(6)a(7) from Robert Price, Jun 04 2011


STATUS

approved



