OFFSET
1,1
COMMENTS
See A181409 for the largest k.
PROG
(PARI) isok(n) = {for (k=ceil(n/2), n-1, p = 2^n - 2^k - 1 ; if (isprime(p) && isprime(p+2), return(1)); ); } \\ Michel Marcus, Dec 23 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Jan 28 2011
STATUS
approved