

A092558


Numbers n such that 2^n +/ 1 are both semiprimes.


6




OFFSET

1,1


COMMENTS

Intersection of A092559 and A085724.
a(7), if it exists, is at least 41519.  Charles R Greathouse IV, Jun 05 2013


LINKS

Table of n, a(n) for n=1..6.


EXAMPLE

11 is a member because 2^111=23*89 and 2^11+1=3*683.


PROG

(PARI) is(n)=isprime(n) && n>7 && ispseudoprime((2^n+1)/3) && bigomega(2^n1)==2 \\ Charles R Greathouse IV, Jun 05 2013


CROSSREFS

Subsequence of A000040.
Cf. A092559, A085724, A092561, A092562.
Sequence in context: A077707 A081981 A081982 * A294255 A088777 A041238
Adjacent sequences: A092555 A092556 A092557 * A092559 A092560 A092561


KEYWORD

nonn


AUTHOR

Zak Seidov, Feb 27 2004


EXTENSIONS

a(6) from Robert G. Wilson v, Apr 18 2006


STATUS

approved



