Linked from
The 15 pages that link to Pascal's triangle, each with the reason it gives.
Binomial theoremRelated: Its rows list the coefficients in successive binomial expansions.
Recurrence relationRelated: Its adjacent-entry rule is a recurrence across rows.
Triangular numberRelated: Its third diagonal contains the triangular numbers.
Jia XianRelated: Jia Xian's arrangement gave an early Chinese presentation of this pattern.