Odd Square is Eight Triangles Plus One/Historical Note

Historical Note on Odd Square is Eight Triangles Plus One

This result, according to David Wells in Curious and Interesting Numbers in $1986$, was known to Diophantus of Alexandria.

However, David M. Burton in his Elementary Number Theory, revised ed. of $1980$, attributes the result to Plutarch, circa $100$ C.E.

Sources

• 1980: David M. Burton: Elementary Number Theory (revised ed.) ... (previous) ... (next): Chapter $1$: Some Preliminary Considerations: $1.3$ Early Number Theory: Problems $1.3$: $1 \ \text {(b)}$
• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $15$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $15$