slow "IN" clause

I have a slow sql:
SELECT * FROM mytable WHERE id IN (1,3,5,7,....3k here...);
mytable is about 10k rows.

if don't use the "IN" clause, it will cost 0,11 second, otherwise it
will cost 2.x second
I guess pg use linear search to deal with IN clause, is there any way
to let pg use other search method with IN clause? (ex.Binary Search or
hash Search)