find the missing number in the following sequence 13,7,18,10,5 -9,1,12,6?

I can't see any obvious pattern

To find the missing number in the given sequence, let's first analyze the pattern:

Starting with 13, each subsequent number seems to alternate between subtracting a decreasing value and adding an increasing value.

First, let's subtract a decreasing value:

13 - 6 = 7
7 - 11 = -4
-4 - 8 = -12

Now, let's add an increasing value:

-12 + 13 = 1
1 + 17 = 18
18 + 9 = 27

The sequence so far is: 13, 7, 18, 10, 5, -9, 1, 12, 6, 27

Now, if we continue subtracting a decreasing value:

27 - 4 = 23

Thus, the missing number in the sequence is 23.