Definition: A sequence {an} converges to L if, for any number ϵ>0, there exists an integer N such that
|an−L|<ϵ
whenever n>N.
In other words, no matter how close to the limit we want to get (ϵ-close), we will eventually get and stay there, where "eventually" means "after N steps".
Limit Laws
The limit laws for sequences are almost exactly the same as the limit laws for functions. For instance, if the sequence {an} converges to L and the sequence {bn} converges to M, then
{an+bn} converges to L+M
{an−bn} converges to L−M
{anbn} converges to LM
{anbn} converges to LM as long as M≠0, and
If c is a constant, {can} converges to cL.
As a result, the sum, difference, product and ratio of two convergent sequences automatically converge (if we're not dividing by numbers close to zero), as do multiples of convergent sequences.