OFFSET
1,3
COMMENTS
Up to n=6601, a(n) = 0 for 916 values of n and a(n) >= n/2 for 4574 values of n.
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..10000
MATHEMATICA
Table[k=n; While[k>0 && ! PrimeQ[2^n+2^k+1], k--]; k, {n, 100}]
PROG
(PARI) A179760(n)={forstep(i=n, 1, -1, if(isprime(2^n+2^i+1), return(i))); return(0)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Jan 12 2011
STATUS
approved