Question 1176631
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The question is impossible to answer; any number there would make a valid sequence.<br>
Presumably the author of the problem had a particular pattern in mind which leads to a specific missing number.  But there are almost certainly very different patterns that fit the given numbers and yield a very different missing number.<br>
So the ONLY way to find the RIGHT answer to ANY problem like this is to ask the author of the problem what the answer is.<br>
Therefore, math can't solve this problem; only mind reading can.<br>
Spend as much (or as little) time as you want looking at the problem to see if you can find a logical pattern that produces an answer for the missing number.  But realize while you are doing that that any answer you come up with might not be "right".<br>