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

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

Offset: 1

Author

Juri-Stepan Gerasimov, Oct 02 2011

Keywords

• nonn

Comments

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

Examples

			a(1)=2 because 2 is a prime and (2-1)^2*2^2-1=3 is a prime,
a(2)=3 because 3 is a prime and (3-1)^2*2^3-1=31 is a prime,
a(3)=19 because 19 is a prime and (19-1)^2*2^19-1=169869313 is a prime,
a(4)=29 because 29 is a prime and (29-1)^2*2^29-1=420906795007 is a prime.
		

Programs

Mathematica

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