Number Series/ Arithmetic sequence

Question

How do you solve number series or sequence where the values alternate between adding a number and subtracting a number?

For example: Find the 30th term in the sequence.

6,2,7,3,8,4,9..

Notice the complex pattern is subtracting 4 then adding 5. How do I go about finding the rule so that I am able to find any term number asked for? What are these kind kind of sequence specifically called?

Answer 1

the sequence is 2 alternating sequences

6,7,8, 9, ...for odd terms

and 2,3,4,5, ...for even terms

30th term is even and is the 15th term of the even terms = 16

2,3,4,5,6

7,8,9,10,11

12,13,14,15, 16= 30th term of the given sequence