Solving the Sequence
Identifying the Pattern
The key insight is to split each number into two parts and track how those parts evolve:



Term
Split
First Part
Second Part



31
3 | 1
3
1


63
6 | 3
6
3


(13)
(misdirection)




129
12 | 9
12
9


2427
24 | 27
24
27


The two parts follow clean rules:

First part: 3, 6, 12, 24, 48, … → ×2 each step (i.e., 3·2ⁿ)
Second part: 1, 3, 9, 27, 81, … → ×3 each step (i.e., 3ⁿ)

Each term is formed by concatenating the first and second parts.
The Next Term

First part: 24 × 2 = 48
Second part: 27 × 3 = 81
Concatenation: 4881

The Answer
$$\boxed{4881}$$
(The 13 is a red herring — it's 31 reversed, inserted to disguise the core pattern.)