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A196446 Numbers n such that both n and (n-1)^2*2^n-1 are primes. 1

%I

%S 2,3,19,29,43,61,79,109,151,167,2311

%N Numbers n such that both n and (n-1)^2*2^n-1 are primes.

%C Primes p such that (p-1)^2*2^p-1 is also prime.

%e a(1)=2 because 2 is a prime and (2-1)^2*2^2-1=3 is a prime,

%e a(2)=3 because 3 is a prime and (3-1)^2*2^3-1=31 is a prime,

%e a(3)=19 because 19 is a prime and (19-1)^2*2^19-1=169869313 is a prime,

%e a(4)=29 because 29 is a prime and (29-1)^2*2^29-1=420906795007 is a prime.

%t Select[Prime[Range[40]],PrimeQ[(#-1)^2 2^#-1]&] (* The program generates the first 10 terms *) (* _Harvey P. Dale_, Sep 06 2017 *)

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Oct 02 2011

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Last modified August 12 05:33 EDT 2020. Contains 336438 sequences. (Running on oeis4.)