

A128335


Numbers n such that (4^n + 5^n)/9 is prime.


31



5, 7, 19, 29, 61, 137, 883, 1381, 1823, 5227, 25561, 29537, 300893
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OFFSET

1,1


COMMENTS

All terms are primes.


LINKS

Table of n, a(n) for n=1..13.
Top probable primes of the form (5^p+4^p)/9


MATHEMATICA

k=4; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]


PROG

(PARI) forprime(p=3, 1e4, if(ispseudoprime((5^p+4^p)/9), print1(p", "))) \\ Charles R Greathouse IV, Jul 16, 2011


CROSSREFS

Sequence in context: A255490 A045446 A106074 * A023246 A022889 A001562
Adjacent sequences: A128332 A128333 A128334 * A128336 A128337 A128338


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Feb 27 2007


EXTENSIONS

3 more terms from Ryan Propper, Feb 06 2008
Two more terms from Ryan Propper, May 02 2010
New term 300893 found by JeanLouis Charton in November 2011 corresponding to a probable prime with 210315 digits.


STATUS

approved



