Add up the first ten cubes: 1+8+27+64+125+216+343+512+729+1000 = 3025. Now compute (1+2+3+...+10)² = 55² = 3025. They're equal — and they're always equal, for any n. There's no obvious arithmetic reason that should be true. Aryabhatiya II.22 (499 CE) states the identity in a single Sanskrit verse, alongside the equally clean Σi² = n(n+1)(2n+1)/6. Alhazen and Fermat rediscover them in pieces; Faulhaber gives the systematic European treatment in 1631.