45, 6, 13, 26, ?, 70

The pattern in the sequence appears to be alternating between subtracting and adding.

Starting with 45, if you subtract 39 you get 6.

Then, if you add 7 to 6, you get 13.

Next, if you add 13 to 13, you get 26.

Following the pattern, the next operation should be subtraction. However, since the next number in the sequence (70) is larger than the current number (26), it seems like the pattern might actually be to subtract a negative number (which is equivalent to addition).

So, if we subtract -44 from 26, we get 70.

Therefore, the missing number in the sequence should be 70 - 26 = 44.