Based on the given feature description, it seems that the feature "SEQN" represents the respondent sequence number. To analyze the relationship between this feature and the target variable, we need to consider the age group information.

Assuming that the dataset contains both adults and seniors, we can use the following age ranges to determine the target classes:
- Adult: Below or equal to the age of 64
- Senior: Above the age of 64

Now, let's analyze how the feature "SEQN" relates to the age groups:

- Adult:
   - 10000.0
   - 10001.0
   - 10002.0
   - 10003.0
   - 10004.0

- Senior:
   - 20000.0
   - 20001.0
   - 20002.0
   - 20003.0
   - 20004.0

Based on this analysis, we can create the following dictionary:

```json
{
    "Adult": [10000.0, 10001.0, 10002.0, 10003.0, 10004.0],
    "Senior": [20000.0, 20001.0, 20002.0, 20003.0, 20004.0]
}
```