How many {decays to} are to/by {helium-4} ?
What is the time frame for the decay of helium-4.
When does helium-4 decay?
SELECT ( COUNT ( ?s ) AS ?w ) { ?s property:decays_to resource:helium-4 }
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/P816> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q1151346 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P816 wd:Q1151346 }
6