OFFSET
1,1
COMMENTS
a(n) is the greater of primes (p,q) in representations of a power of 3 in Lemoine-Levy's form p+2q (see A046927)
If 3^n=p+2q, then 3^(n-1)<=max(p,q)<3^n. Therefore the sets of greater primes for different powers of 3 do not intersect.
FORMULA
If A(x) is the counting function of a(n)<=x, then A(x)=O(xloglogx/(logx)^2).
EXAMPLE
27=5+2*11=13+2*7=17+2*5=23+2*2, so that 11,13,17 and 23 are in the sequence.
PROG
(PARI) aa(n)={my(v=[]); forprime(p=2, n\2, q=n-p*2; if(isprime(q), v=concat(v, (max(p, q))))); vecsort(v, , 8)};
for(n=2, 7, v=aa(3^n); for(i=1, #v, print1(v[i], ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Dec 05 2008, Dec 12 2008
EXTENSIONS
Program and editing by Charles R Greathouse IV, Nov 02 2009
STATUS
approved