Owlet puzzle #99
Released Monday, October 12, 2026 UTC
2025
the answer for puzzle #99
The five clues
- A four-digit square year.
- A recent calendar year.
- A perfect square equal to the sum of the first nine cubes.
- (20 + 25)² = this number.
- The next square year after 1936 (44²).
Backstory
2025 = 45² = (1+2+…+9)² = 1³+2³+…+9³ by Nicomachus's theorem, so it's the sum of the first nine cubes. Also 2025 = 40² + 5², a sum of two squares. In 2025 CE, this coincidence of year-as-Nicomachus-sum will occur only once per millennium — the next such year is 3025.
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