

A128025


Numbers k such that (8^k  3^k)/5 is prime.


28




OFFSET

1,1


COMMENTS

All terms are primes.
Verified the first 8 terms in sequence. Also, the next number in the sequence, if one exists is > 43691.  Robert Price, Mar 16 2010
a(10) > 10^5.  Robert Price, Jul 27 2011


LINKS

Table of n, a(n) for n=1..9.


MATHEMATICA

k=5; Select[ Prime[ Range[1, 200] ], PrimeQ[ ((k+3)^#  3^#)/k ]& ]


PROG

(PARI) is(n)=isprime((8^n3^n)/5) \\ Charles R Greathouse IV, Feb 17 2017


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, A128026, A128027, A128028, A128029, A128030, A128031, A128032.
Sequence in context: A195354 A244638 A113165 * A092064 A152609 A298943
Adjacent sequences: A128022 A128023 A128024 * A128026 A128027 A128028


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Feb 11 2007


EXTENSIONS

9227 from Farideh Firoozbakht, Apr 08 2007
a(9)=43891 from Robert Price, Jul 27 2011


STATUS

approved



