照suttacentral.net 說法經號是以PTS為主，PTS的AN是三段式經號，但簡化的 二段
式經號AN 1.17是更廣泛的被接受使用，故AN例外採用二段式經號，但刮號附上PTS的
三段式經號
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