Yes, number 1 & 2 are interchangeable. Number 3 is not, as it is grammatically incorrect. In number 1, the speaker refers to "each" in order to highlight the fact that the two sequences are independent and separate from each other, even though both sequences share something in common.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Danny-K Number 3 is incorrect because "are an example" mixes plural and singular.I remember seeing many native American English speaker using something like this. Even I found it a bit weird initially (my basic English training was based on British English), but looks like Americans are fine with that expression. For example, in