# [J], 32 bytes

    (^1+15=])@i.~&'(^1+15=])@i.~&'''

[Try it online!][TIO-jd0djd9m]

Find each character in the string `(^1+15=])@i.~&'` Raise the index to the power of 1+(equals 15): if the character doesn’t exist, the index will equal the length of the string, in that case square the index.

[J]: http://jsoftware.com/
[TIO-jd0djd9m]: https://tio.run/##y/r/389JT@FR22QDBQUQZQqhDA0glCmYMoLwjKCSxoZcabZ6ChpxhtqGpraxmg6ZenVq6mhcdfX/qckZ@QppCsUlKZl5Cob/gUqAKpSB8up6dQA "J – Try It Online"