30.
The series can be generated by:
t(n) = (-n3 + 3n2 - 56n + 510)/6 for n = 1, 2, 3, ...
33
54 The numbers are in pairs with the second number being the reverse of the first number.
57
70
-57
-57
-57
The next number is 49+8 = 57
-57
The difference between one number and the next in the sequence is decreasing by 9 each time. Therefore, the difference between -4 and the next number will be equal to 62 - 9 = 53. The next number is therefore equal to -4 - 53 = -57.
-57
The pattern is add three and then multiply by three. The next number is 174.