CREATE TABLE table_name_41 (population__1960_ INT, county VARCHAR, population__2000_ VARCHAR)

What was Oslo's population in 1960, with a population of 507,467 in 2000?
SELECT AVG(population__1960_) FROM table_name_41 WHERE county = "oslo" AND population__2000_ > 507 OFFSET 467
SELECT AVG("population__1960_") FROM "table_name_41" WHERE "county" = "oslo" AND "population__2000_" > 507 OFFSET 467