APL (Dyalog), 7 5 bytes
2 bytes saved thanks to @Mego
+.×⍨⍳
How?
⍳ - range
+.× - inner product (a +.× b → +/ a × b)
⍨ - with itself (on both sides)
| 2 of 3 | added 42 characters in body | ||||
APL (Dyalog), |
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| 2 of 3 | added 42 characters in body | ||||
APL (Dyalog),
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