I know that “factorial” means the **product ** of all the positive integers from 1 to a given number.
What is the term for the **sum **of those numbers?
Thanks.
The triangular numbers.
Or just “the summation of all integers from 1 to n”
There is no standard term for the operation. The triangular numbers are the sequence of sums, but you can’t use it like “n triangle”.
Because you can just say n(n+1)/2, I doubt there’s ever been a need for another name. (As ultrafilter said, “triangular numbers” refers to the sequence, rather than the operation.)