A057469 Prime numbers k such that (2^k + 3^k)/5 is prime.
3, 7, 11, 83, 149, 223, 599, 647, 1373, 8423, 149497, 388897, 531611, 2052329
Offset: 1
Crossrefs
Cf. A127908 (primes of the form (3^k+2^k)/5).
Programs
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Magma
[p: p in [3..1000] | IsPrime(p) and IsPrime((2^p + 3^p) div 5)]; // Jinyuan Wang, Dec 22 2019
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Mathematica
Do[ If[ PrimeQ[ n ], If[ PrimeQ[ (3^n + 2^n)/5 ], Print[ n ] ] ], {n, 0, 6270} ] -
PARI
is(n)=isprime(n) && ispseudoprime((2^n + 3^n)/5) \\ Charles R Greathouse IV, Apr 28 2015
Extensions
More terms from Kamil Duszenko (kdusz(AT)wp.pl), Apr 11 2003
Definition corrected by Alexander Adamchuk, Feb 06 2007
a(11) corresponding to a probable prime with 71328 digits from Jean-Louis Charton, Oct 14 2010
a(12) corresponding to a probable prime with 185551 digits from Jean-Louis Charton, Sep 18 2011
a(13) corresponding to a probable prime with 253643 digits from Ryan Propper, Dec 10 2023
a(14) corresponding to a probable prime with 979210 digits from Ryan Propper, Dec 10 2023