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A082182 Numbers n such that (5^n-2^n)/3 is prime. 21
2, 5, 7, 13, 19, 37, 59, 67, 79, 307, 331, 599, 1301, 12263, 12589, 18443, 20149, 27983 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No other terms less than 100000. - Robert Price, Apr 06 2012

LINKS

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

User group for the PrimeForm program.

EXAMPLE

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

MATHEMATICA

a={}; Do[p=(5^n-2^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^p-2^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

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Last modified December 3 21:14 EST 2016. Contains 278745 sequences.