# odd number theorem

> theorem in strong gravitational lensing stating that the number of multiple images produced by a bounded transparent lens must be odd

**Wikidata**: [Q280116](https://www.wikidata.org/wiki/Q280116)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Odd_number_theorem)  
**Source**: https://4ort.xyz/entity/odd-number-theorem