OFFSET
1,2
COMMENTS
As n increases sum a(n) from 1 to n / n tends to 2.66.
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..3000
PROG
(PARI) a(n) = sum(k=1, n, isprime((2^k+1)*2^n-1)); \\ Michel Marcus, Sep 21 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Oct 11 2011
STATUS
approved