A156895 Primes of the form 1 + Product_{j=0..k} (2^j + 1).

3, 7, 31, 271, 4591, 151471, 9845551, 326409519151, 16455349947998422816223361143099916435126171767057238357700938736968751

Offset: 1

Author

J. M. Bergot, Feb 17 2009

Keywords

• nonn

Comments

10th term has 150 digits. - Emeric Deutsch, Mar 07 2009

Primes of the form 1 + A028361(k), any k > 0. - R. J. Mathar, Jul 10 2011

Examples

			(2^0 + 1)*(2^1 + 1)*(2^2 + 1)*(2^3 + 1)*(2^4 + 1) + 1 = 2*3*5*9*17 + 1 = 4591.
		

Crossrefs

Cf. A028361.

Programs

Maple

a := proc (n) if isprime(1+product(2^k+1, k = 0 .. n)) = true then 1+product(2^k+1, k = 0 .. n) else end if end proc: seq(a(n), n = 0 .. 40); # Emeric Deutsch, Mar 07 2009

Mathematica

Select[Table[Product[2^j+1,{j,0,k}],{k,0,30}]+1,PrimeQ] (* Harvey P. Dale, Aug 01 2019 *)

Extensions

a(9) from Emeric Deutsch, Mar 07 2009