odd number theorem
theorem in strong gravitational lensing stating that the number of multiple images produced by a bounded transparent lens must be odd
en-US/ˈɑd ˈnʌmbɚ ˈθɪɹəm/
en-GB/ˈɒd ˈnʌmbə ˈθɪəɹəm/
theorem in strong gravitational lensing stating that the number of multiple images produced by a bounded transparent lens must be odd