2 normal types of sequences:
1. arythmetic sequences: each term is the same distance to the next term, example, 2,4,6,8, distance is 2
2. geometric sequences: the ratio of consecutive terms is the same, example: 2,4,8,16, ratio is 4:2=2:1, 2/1=2
the nth term is denoted by

the first term is represented by

for arythmetic sequences, the nth tem is

where d=distance between each term
for geometric sequences the nth term is
[tex] a_{n}=a_{1}r^{n-1} where r=ratio betwen consecutive terms