Some journals publish articles with article numbers or an eLocator instead of traditional page numbers. In these journals, each article starts with page 1. These articles are formatted slightly differently in the references.
In APA Style (7th ed.), if the article has an article number or eLocator, instead of including the page range, write the word "Article" and then the article number followed by a period.
For example
from Journal Article Reference Checklist
In AMA Style (11th ed.), if the article has an article number or eLocator, replace the page numbers with the article number or eLocator.
For example
Wang G, Hu FB, Mistry KB, et al. Association between maternal prepregnancy body mass index and plasma folate concentrations with child metabolic health. JAMA Pediatr. 2016;170(8):e160845. doi:10.1001/jamapediatrics.2016.0845
from AMA Manual of Style (11th ed)