A119550 Prime numbers of the form 2^(2^n) + 2^n - 1.

2, 5, 19, 263, 65551

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Formula

Define F(n) = 2^(2^n)+1 = n-th Fermat number, M(n) = 2^n-1 = the n-th Mersenne number. Then we are considering the numbers f(n) = F(n)+M(n)-1 = 2^(2^n) + 2^n - 1 (cf. A119563).

Example

F(2)= 2^(2^2)+1 = 17, M(2) = 2^2-1 = 3, F(2)+ M(2)-1 = 19 is prime, so 2 is a member.

Prog

(PARI) fmp3(n)=for(x=0, n, y=2^(2^x)+2^x-1; if(ispseudoprime(y), print1(y", ")))

Crossrefs

Cf. A119563, A119564.

Sequence in context: A080280 A218386 A055813 * A119563 A270398 A269997

Adjacent sequences: A119547 A119548 A119549 * A119551 A119552 A119553

Keyword

nonn,more,less

Author

Cino Hilliard, May 31 2006

Extensions

Edited by N. J. A. Sloane, Jun 03 2006

Definition corrected by Stefan Steinerberger, Jun 10 2007

Status

approved