37
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-243
I think its 40
The series is n3: 13, 23, 33 ...The next number is 216.
Since there is 16 between the first and second terms and 2 x 16 (32) between the second and third terms, then the forth term should be 3 x 16 (48) higher. The series is 11 27 59 107 171 251...
Possibly -218, using Un = (-27n4 + 314n3 - 1260n2 + 2041n - 1026)/6 where n = 1, 2, 3, ...