Since I have spent quiet a few days on this one, needed to post something I finally got working(at least in my own head)
The Mystery Sequence is
$733,\space \space 716,\space \space 645,\space \space 565,\space \space 324,\space \space 276,\space \space 77,\space \space 75,\space \space 64,\space \space 56,\space \space 48,\space \space 38$
Pattern is
We need to take the sum of all the digits which leads to 13 14 15 16 9 15 14 13 10 11 Now, lets place them vertically to see how they look. When done, we can see the following sequence -
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.
.
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13 (Set n-2)
14 (Set n-2) $\Leftarrow$ DESCENDING ORDER
15 (Set n-2)
16 (Set n-2)
-> 9 (Set n-2 begins)
15 (Set n-1)
14 (Set n-1) $\Leftarrow$ ASCENDING ORDER
12 (Set n-1)
-> 10 (Set n-1 begins)
11 (Set n)
12 (Set n) $\Leftarrow$ DESCENDING ORDER
-> 11 (Set n begins) BEGIN HERE $\Uparrow$
Which means we need two numbers whose sum gives 12 and 11. For 12, the next number we have is 48 and for 11, the next number we have is 38. Since, I am assuming -> to be the start, there cannot be any numbers beyond that. I am not good at formatting and I suck at mathematical formatting so bear with me on this... Well, I am satisfied with that thing above :)