1³+2³+3³+4³+5³+6³+…+n³=(1+2+3+4+5+6+…+n)²

Proof:
Arranging 1³+2³+3³+4³+5³+6³+…+n³ in the plane: 1×1²+2×2²+3×3²+4×4²+5×5²+6×6²+…+nxn²
The even squares overlap (🟨) but also leave uncovered gaps (🟥) and 🟨=🟥 pic.twitter.com/To8e3DlW6a

— Fermat's Library (@fermatslibrary) October 20, 2021