SQL Anywhere contains an sa_rowgenerator stored procedure, which can be used for this purpose. For example:
select row_num from sa_rowgenerator( 1, 100 )
returns a result set of 100 rows from 1 to 100 inclusive. A link to the documentation (for version 12.0.1) is here.
Disclaimer: I work for SAP/Sybase in the SQL Anywhere engineering.