Answer:
Normally, the term infinite sequence refers to a sequence that is infinite in one direction, and finite in the other-the sequence has a first element, but no final element. Such a sequence is called a singly infinite sequence or a one-sided infinite sequence. A set of all natural numbers (1, 2, 3,.........) is singly infinite. In contrast, a sequence that is infinite in both directions-i.e. that has neither a first nor a final element-is called a bi-infinite sequence, two-way infinite sequence, or doubly infinite sequence. A set of all integers (..., -4, -2, 0, 2, 4, 6, 8, ...), is bi infinite
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