We can see that the sequence is formed by adding 4 each time
8
8+4=12
8+4+4= 16
8+4+4+4=20
and so on
Hence the pattern is 4 gets added to the previous number
when we come across such a pattern, where a same number is added everytime, it is called an arithmetic sequence
The first term is denoted by a
and the number that is added every time is denoted by d
the arithmetic sequence is denoted by
a, a+d, a+2d, a+3d and so on
