How many {named after} are for {September} ?
Which is the number of people that are named after the month of September?
How many people are named after the month of September?
SELECT ( COUNT ( ?w ) AS ?o ) { resource:September property:named_after ?w }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q123> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P138> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q123 wdt:P138 ?obj }
5