Was a sequel of a film written by M0 and produced by M1
SELECT count(*) WHERE {
?x0 ns:film.film.prequel ?x1 .
?x0 ns:film.film.produced_by|ns:film.film.production_companies M1 .
?x0 ns:film.film.written_by M0 .
?x1 a ns:film.film
}