Perhaps you thought that because ein doesn't have an ending for neuter nominative?
Adjectives don't inflect exactly like ein, though.
The endings they take depend on whether there's something in front of them, and if so, what.
After a definite article (der, die, das etc.), they take weak inflection -- this is -e in the nominative singular for all genders, and also for the accusative singular for neuter and feminine (where nominative = accusative always). All other combinations are -en in weak inflection (i.e. masculine accusative singular; all cases in the plural; and genitive and dative of all genders).