I agree with remi. because A is article. follow article is Countable Noun. and swedish is a adjective.

Actually, you would not add "a" if you were saying somebody is swedish. You would say "He is Swedish," just as the same as you would say "He is Chinese," or "She is Russian." The only time you would add "a" would be if you were saying "He is a Swede," which is just a variation of "He is Swedish." Another similar instance where you would add "a" would be if you were saying something "He is a Frenchman." Hope this helps!