4X4X4X4X4X4X4X4=65536 for a single strand, as in a primer. Twice this number if you include the complementary antisense strand (each strand being a different molecule), but I suppose some of the complementary strands would be the same as some of the sense strands, so the actual number of different molecules would be less than 131,072. Anyone care to tackle this issue?
Multiplying by 2 does not make sense, since the antisense molecule is constrained by the sense one, there is only 4 choice for each pair so 4^8 is the answer.
