# [APL (Dyalog)], 7 bytes

<!-- language-all: lang-apl -->

    +/(×⍨⍳)

[Try it online!][TIO-j8vk7rlp]

**How?**

`⍳` - range (`1 2 3 4 5`)

`×⍨` - multiply with itself (vectorized, `1 4 9 16 25`)

`+/` - sum (`55`)

[APL (Dyalog)]: https://www.dyalog.com/
[TIO-j8vk7rlp]: https://tio.run/##SyzI0U2pTMzJT///P@1R2wRtfY3D0x/1rnjUu1kTKKJwCMQyNAAA "APL (Dyalog Unicode) – Try It Online"