Note that this is the wrong rule for English which uses nb<>1.
This is for this reason that the PO file format uses the number of items to support plural forms since languages tend to have many rules for plural.
For instance English uses a special rule for ordinal depending on n mod 10. Polish has a similar rule except that it has two plural forms (one for 2-4 and another for 5-9). In general, dual is also not unheard of as a second plural form, for instance in Slovene.