To solve the problem, we first clarify the sequence generation rules and count the terms until we encounter 1 again (including both the initial and final 1):

Step 1: Generate the sequence

The sequence starts with 1 (term 1).

• Term 1: 1 (odd → next term = 3×1 +1 =4)
• Term 2:4 (even → next term=4/2=2)
• Term3:2 (even → next term=2/2=1)
• Term4:1 (stop here, as we've encountered 1 again)

Step2: Count the terms

The sequence is [1,4,2,1], which has 4 terms.

Answer: 4.

$\boxed{4}$

作者声明:本文包含人工智能生成内容。