How many {production company} are to/by {HBO} ?
How many production companies are by HBO?
SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P272 wd:Q23633 }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P272> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q23633 .
} 

HBO has what number of production companies?