a(k) = kth positive integer containing an even/odd number of prime factors (with repetition) according as k is odd/even respectively. a(a(k)) = a(k+1). a(1) is not defined.
conjecture: these are disjoint sets whose union is Z+
EXAMPLE
a(2)= 6, the second integer containing an even number of prime factors, 2,3. a(6)= 11, the sixth integer containing an odd number of primes, 11. The next sequence begins with 3 and is 3,9,17,36,...
