Option 1: In the Data transform follow the below steps.
Set the start index and end index based on the value you enter in UI to a property or param and call another DT (DT2) which does the below steps
When Start index < End Index
String value = String value + “,”+ Start Index (creating the string which you need)
Start index = Start index + 1 (Incrementing the index for next loop)
Set the Data transform name (DT2) in a parameter
Call the data transform using the parameter set in above step
Caution: Misconfiguration will leads to infinite loop. So be cautious. Do all validations (like end index should be greater than start index) before you run the DT.
Option 2: Execute a activity which can use for loop to generate the sequence.