The next number could be 25.
+3, +6, +9, +12 etc.
The pattern alternates between two sequences: one decreasing by 1 (18, 13) and the other decreasing by 2 (4, 6). Following this pattern, the next number after 6 should be 3 (6 - 3), and the next number after 13 should be 12 (13 - 1). Thus, the next two numbers in the sequence are 12 and 3.
The pattern is - 5 then +2. 2 and 4 are the next numbers in the series.
-2
18 b/c the pattern is +1,+2,+3...
16.
The rule of this pattern is -2 + 6 +4 so the next number would be 16.
22
2, the pattern is -5 then plus 2 repeated, therefore 7 - 5 = 2
1 2 3 4 .12 & .13 & .15 & .18 & .22
The pattern is add 2, add 4, add 6, add 2, add 4, add 6 and so forth. Based on this pattern the next number is 39.
I think that the next number in this pattern is twelve. I think that the pattern is 1/2, 2/3. 3/4, 4/5 and so on.
The next number in the series 2-4-3-9-4 is 16. 2 squared is 4, 3 squared is 9, 4 squared is 16