Question 1185085
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There is no mathematics in this or any other similar problem.<br>
Many different logical rules will produce this set of first numbers in the sequence; but those different rules will very likely produce different next numbers.<br>
Technically, the answers to the two questions are these:
Question: What would be the next number? Answer: Any number you want.
Question: Why? Answer: Because any next number makes a valid sequence.<br>
The only way to KNOW the CORRECT answers to any problem like this is to ask the author of the problem what the answers are.<br>