51² = (50 + 1)² = 50² + 2 × 50 × 1 + 1² = 2500 + 100 + 1 = 2601
58² = (60 - 2)² = 60² - 2 × 60 × 2 + 2² = 3600 - 240 + 4 = 3364
21²
22²
23²
24²
25²
26²
27²
28²
29²