15. In

the circle, fill in the natural numbers from 1 to 16 (each number must be used exactly once), so that the sum of the numbers in the 4 circles connected by the same straight line is equal. This is called an 8-order magic star, and this equal number is called the magic sum of the 8-order magic star. Therefore, the magic sum of the 8-order magic star is , and continue to complete the following 8-order magic star:



保留源文本的换行和格式，直接输出翻译结果。 

(Note: The last sentence is a note in Chinese and is not part of the translated text. It is provided here for context.)
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