Question: What is the largest n value for 55.6% r1b1c4 (r-v69)?
Schema: create table table_21481509_4 (n integer, r1b1c4__r_v69_ varchar, PRIMARY KEY (n))
SQL: select max(n) from table_21481509_4 where r1b1c4__r_v69_ = "55.6%"