OFFSET
1,2
COMMENTS
omega is the function in A001221. If there are infinitely many Sophie Germain primes (see A005384), then this sequence is infinite. Proof : the numbers of the form 4p are in a subsequence if p and 2p+1 are both primes, because from the property that omega(4p) = 2 and omega (p(2p+1)) = 2, if n = 4p then omega (n+omega(n)) = omega (4p + 2) = omega (2(2p+1)) = 2 = omega (n).
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
12 is in the sequence because omega(12) = 2, omega(12 + 2) = omega(14) = 2.
MATHEMATICA
Select[Range[5*10^2], PrimeNu[#]==PrimeNu[#+PrimeNu[#]]&]
PROG
(PARI) is(n)=my(o=omega(n)); o==omega(n+o) \\ Charles R Greathouse IV, Feb 14 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 14 2012
STATUS
approved