\d+a Unicode decimal digit, repeated at least once
the literal (3210 / 408 / 2016)
A-Zone character from A (6510) to Z (9010) (case sensitive)
+matches at least one character from the set below:
a-zone character from a (9710) to z (12210) (case sensitive)
\d{4}a Unicode decimal digit, repeated exactly 4 times