Aliens have abducted 10,000 people and placed them on a generation ship, a really big one, for the purpose of seeding the stars with our species, which is nice of them. What ratio of men to women should the aliens choose in order to end with an even sex ratio at then end of a journey lasting 500 years?
Assume any form of society you please. Awesome alien tech takes care of all sorts of otherwise intractable problems.
Edit -> More detail:
Our alien friends want to deposit a balanced population on a habitable world before sending the craft back to earth to pick up another load. But to their way of thinking, having excess males when one can impregnate many females is a wasteful extravagance. They are looking for efficient population growth.
Think of chicken husbandry as an analogy if you wish: many hens, one rooster (or in this case, many roosters and many, many hens).