

A082182


Numbers k such that (5^k  2^k)/3 is prime.


21



2, 5, 7, 13, 19, 37, 59, 67, 79, 307, 331, 599, 1301, 12263, 12589, 18443, 20149, 27983
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OFFSET

1,1


COMMENTS

No other terms less than 100000.  Robert Price, Apr 06 2012
All terms are primes. Some of the results were computed using the PrimeFormGW (PFGW) primalitytesting program.  Hugo Pfoertner, Nov 14 2019


LINKS

Table of n, a(n) for n=1..18.
OEIS Wiki, Primes of the form (a^n+b^n)/(a+b) and (a^nb^n)/(ab).


EXAMPLE

Example: a(1)=2 because (5^2  2^2)/3 = (25  4)/3 = 7 is a prime.


MATHEMATICA

a={}; Do[p=(5^n2^n)/3; If[PrimeQ[p], AppendTo[a, n]], {n, 20^2}]; Print[a]; (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)


PROG

(PARI) forprime(p=2, 1e4, if(ispseudoprime((5^p2^p)/3), print1(p", "))) \\ Charles R Greathouse IV, Jul 16, 2011


CROSSREFS

Sequence in context: A175075 A262392 A056985 * A032719 A275287 A261581
Adjacent sequences: A082179 A082180 A082181 * A082183 A082184 A082185


KEYWORD

more,nonn


AUTHOR

Hugo Pfoertner, May 22 2003, Jun 23 2003


EXTENSIONS

20149 from Herman Jamke (hermanjamke(AT)fastmail.fm), May 03 2007
27983 from David Radcliffe, May 28 2007


STATUS

approved



