Editing Look-and-say sequence (section)

=== Digits presence limitation ===
No digits other than 1, 2, and 3 appear in the sequence, unless the seed number contains such a digit or a run of more than three of the same digit.<ref name="Martin2006">
{{cite journal
 |title=Look-and-Say Biochemistry: Exponential RNA and Multistranded DNA
 |first=Oscar
 |last=Martin
 |journal=American Mathematical Monthly
 |year=2006
 |volume=113
 |issue=4
 |pages=289–307	
 |publisher=Mathematical association of America
 |issn=0002-9890
 |url=http://www.uam.es/personal_pdi/ciencias/omartin/Biochem.PDF
 |archiveurl=https://web.archive.org/web/20061224154744/http://www.uam.es/personal_pdi/ciencias/omartin/Biochem.PDF
 |archivedate=2006-12-24
 |accessdate=January 6, 2010
 |doi=10.2307/27641915
|jstor=27641915
 }}</ref>