I'm trying to do a 'Clients per AP' graph with The Dude software using SNMP. After some research, I've found 188.8.131.52.4.1.25053.1.2.2.184.108.40.206.1.15 is the right OID for total number of clients on each AP both form internet and ZD30xx_Syslog_Reference_Guide_9.6.pdf
Now I tried to use 220.127.116.11.4.1.25053.1.2.2.18.104.22.168.1.15 as data source, but nothing comes up.
It's the right OID for current versions, however there are a couple of complications. First, it's an SNMP table, not a single value and depending on the tools you're using they may not be querying it properly. Secondly you need to pull AP details from another table at 22.214.171.124.4.1.25053.1.2.2.126.96.36.199.1.2 and then match the line ID to match name to number of clients.