1 is trivially in the sequence.
Note that any value assumed by phi is assumed at an even argument, since k odd implies phi(k) = phi(2k).
Then 2 is in the sequence, since n = phi(k) and k even imply that 2n = phi(2k).
3 is not in the sequence: 30 = phi(31), but 90 is not in the range of phi.
4 is in the sequence because 2 is (using closure under multiplication).
5 is not in the sequence: 18 = phi(19), but 90 is not in the range of phi.
6 is in the sequence: If n = phi(k) with k even, phi(9k) = 6n if k is a nonmultiple of 3. If k is a multiple of 3, then 6n = phi(6k) since k is a multiple of 6.
7 is not in the sequence: 22 = phi(23), but 154 is not in the range of phi.
8 is in the sequence because 2 is.
