End To End UI test, but nothing to test?

I've completed a simple exercise for a jobs application:

       Numeric Sequence Calculator - Scope 
        Introduction Project  Numeric Sequence Calculator  Goal  As a USER  I want to calculate some numeric sequences  so that [TBD].    Acceptance Criteria  
    1. The software shall be web­based.  
    2. Unit tests shall be written for each functional component of the  software.  
3. An end­to­end UI test shall be written for the software.  
    4. The source shall be saved to a github repository.  
    5. Any instructions required to run the software shall be included in a  README.md file in the root of the repository.  
    6. The repository URL shall be supplied to World Nomads Group 

        User Stories 
    S1 Instructions 
    Story ID  S1 Instructions  Story  As a USER  I want to read some instructions on how to use the application  so that it works first time for me.  Acceptance Criteria  S1.1 The instructions shall be short and to the point. 
    S2 Enter Data Story ID  S2 Enter Data  Story  As a USER  I want to enter a number and initiate the calculation of the numeric  sequences  so that I can view the results.  Acceptance Criteria  S2.1 Input shall accept positive, whole numbers only.  S2.2 Where an input is invalid an error message shall be displayed. 


        © 2014 World Nomads Group Pty Ltd 1 
    S3 Results Story ID  S2 Enter Data  Story  As a USER  I want to view the results of the numeric sequences  so that [TBD].  Acceptance Criteria  
    S3.1 The following numeric sequences shall be displayed:  
    S3.1.1 All numbers up to and including the number entered,  
    S3.1.2 All odd numbers up to and including the number entered,  
    S3.1.3 All even numbers up to and including the number entered,  
    S3.1.4 All numbers up to and including the number entered, except  when,  S3.1.4.1 A number is a multiple of 3 output C, and when,  
    S3.1.4.2 A number is a multiple of 5 output E, and when,   
    S3.1.4.3 A number is a multiple of both 3 and 5 output Z,  
    S3.1.5 All fibonacci number up to and including the number entered.

If you look at number 3 of the requirements: 3. An end­to­end UI test shall be written for the software.

However, I've no experience with end to end UI testing and any examples I find online all test the user logging in.

For this application the user doesnt need to create an account or login. The page loads a text box and a button. The user enters a positive number into the field and clicks the button which displays the results. If they enter a letter or a minus number a pop up message appears. I have performed all the necessary unit tests but...

I am unsure how to write a software test to test this with end to end UI, as I said any examples just test login.

Any help or pointers in the right direction most appreciated.

Could you even point me in the right direction as to what software I should be using?

thanks