##[QBIC](https://drive.google.com/drive/folders/0B0R1Jgqp8Gg4cVJCZkRkdEthZDQ), 18 bytes

    [:|Z=Z+!a$+!b-a+1$

Explanation

    [:|       FOR a = 1 to n
    Z=Z+      Add to Z$ 
    !b$+      a cast of the loop counter as string
    !b-a+1$   and a cast of (n+1) minus the loop counter to string
              Z$ is printed implicitly at the end of QBIC