照suttacentral.net 说法经号是以PTS为主，PTS的AN是三段式经号，但简化的 二段
式经号AN 1.17是更广泛的被接受使用，故AN例外采用二段式经号，但刮号附上PTS的
三段式经号
https://suttacentral.net/sutta_numbering
Sutta Numbering
Pali Sutta Numbers
The numbering of Pali suttas generally follows that used in the Pali Text
Society (PTS) editions. However, there are the following three exceptions.
1) In the first two nip?tas of AN the PTS numbering recognises three
levels of grouping (for nip?ta, vagga, sutta). In such cases we follow the
widely accepted practice of dispensing with the second level. This
involves applying a simple mechanical principle, illustrated in the
following examples:
AN 1.1.6 becomes AN 1.6
AN 1.8.1 becomes AN 1.71
AN 2.2.9 becomes AN 2.19
Nevertheless, in the SuttaCentral tables the PTS sutta number with three
levels is included, within square brackets, after the two-level number.
For example, regardless of whether you type AN 1.71 or AN 1.8.1 into the
“Search” box, the “Search results” screen will show the following:
AN 1.71 [AN 1.8.1] Kaly??amitta AN i 14