The InformixDialect class enhancing the base Dialect class does not overwrite the method supportsPooledSequences().
But Informix supports sequences with min/max values, cache, etc since version 9.4, published years ago.
See http://publib.boulder.ibm.com/infocenter/idshelp/v10/index.jsp?topic=/com.ibm.sqls.doc/sqls264.htm.
see