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Nonnegative numbers n such that 6*2^n-1 is prime.
1

%I #12 Sep 15 2019 07:56:06

%S 0,1,2,3,5,6,10,17,33,37,42,54,63,75,93,102,142,205,215,305,323,390,

%T 457,469,826,1273,3275,4203,5133,7558,12675,14897,18122,18818,25689,

%U 26458,41627,51386,71782,80329,85686,88170,97062

%N Nonnegative numbers n such that 6*2^n-1 is prime.

%C The associated primes are in A007505.

%F a(n) = A002235(n+1)-1. - _R. J. Mathar_, Aug 17 2009

%e n=0 is in the sequence because 6*2^0-1=5 is prime. n=1 is in the sequence because 6*2^1-1=11 is prime.

%o (PARI) is(n)=ispseudoprime(6*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A157341.

%K nonn

%O 1,3

%A _Vincenzo Librandi_, Aug 15 2009

%E Extended by _R. J. Mathar_, Aug 17 2009

%E a(28)-a(43) from _Donovan Johnson_, Jul 09 2010