GNU gettext uses this plural form definition for the Czech language:

nplurals=3; plural=(n%10==1 && n%100!=11 ? 0 : n%10>=2 && n%10<=4 && (n%100<10
|| n%100>=20) ? 1 : 2)

I believe it is wrong and should be changed for following reasons:
1) http://www.ujc.cas.cz/poradna/odpo.html#dveste (czech only, sorry)
   It enforces a language rule, which is not mandatory since 1970'.
   It is not incorrect (its use is still optional), however it sounds
   somewhat archaic today. According to the language institute of the Academy
   of Sciences of the Czech Republic (the czech link above) it is:
   "more common and more natural to NOT use this rule"

2) Its use induces problems. Many (probably most) translators do not expect
   use of this rule. Then they translate the first plural form as it would
   be used only for singular (1 item exactly), not using a variable "%n"
   but literal string as "1", "one" or similar. Then, bugs like this one
   happen: http://bugs.kde.org/show_bug.cgi?id=114283

I propose following definition (modern Czech language, not inducing described
problems):

nplurals=3; plural=(n==1) ? 0 : (n>=2 && n<=4) ? 1 : 2;