Editing Triangular number (section)

==Alternative name==
By analogy with the [[factorial]] function, a product whose factors are the integers from 1 to&nbsp;{{mvar|n}}, [[Donald Knuth]] proposed the name '''Termial function''',<ref>{{TAOCP|volume=1|edition=3|pages=48}}</ref> with the notation {{mvar|n}}? for the sum whose terms are the integers from 1 to&nbsp;{{mvar|n}} (the {{mvar|n}}th triangular number).  Although some other sources use this name and notation,<ref>{{citation | last = Stone | first = John David | doi = 10.1007/978-3-662-57970-1 | page = 282 | publisher = Springer | title = Algorithms for Functional Programming | year = 2018| isbn = 978-3-662-57968-8 | s2cid = 53079729 }}</ref> they are not in wide use.