As U{n} = (-47n⁴ + 598n³ - 2533n² + 4190n - 1992)/24
The next term U5 is (-47 × 5⁴ + 598 × 5³ - 2533 × 5² + 4190 × 5 - 1992)/24 = 42
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Alternatively, it may be two arithmetic sequences interlaced: 9, 5, -1, ... interlaced with 12, 20, 28, ..., ie the sequence is {9, 12, 5, 20, -1, 28, ...} making the next term -1.
In fact, you can have ANY number you want to come next. Give me a number and I'll give you a formula that gives that number, eg:
U{n} = (-45n⁴ + 514n³ - 2019n² + 3170n - 1512)/12
→U5 = (-45 × 5⁴ + 514 × 5³ - 2019 × 5² + 3170 × 5 - 1512)/12 = -1
10
42
16
24
10
20
Think it's 30...then 20
The sequence changes by multiplying with different numbers: from 3 to -6 (* -2), -6 to 12 (* -2), 12 to 4 (* 0.33), and 4 to 20 (* 5). If we continue this pattern, 20 multiplied by 0.5 gives us 10. So, the next number is 10.
20 is the next number greater than 19. The next prime number greater than 19 is 23.
92 - 18 = 72 72 - 16 = 56 56 - 14 = 42 42 - 12 = 30 30 - 10 = 20 20 is the next number in the sequence.
37
20