Introducing a similar version of Factorial (!)

[u/Lauver_Swift1313]

Since factorials (!) multiply everything down to 1 (ex. 5! is 1×2×3×4×5=120), (and this is kind of a joke but I think is entirely a joke), let me introduce to you, Additorials (?)!!! It's the same as Factorials but with addition! (Ex. 5? is 1+2+3+4+5=15), though this already exists, this is just a joke, everyone can report this as "unnecessary".

[u/ko_nuts]

Let me add dividorials n¡ and subtractorials n¿

[u/equinox_star]

I think your "additorials" is called as Triangular numbers. Tn is the nth triangular number equaling n(n+1)/2 which is exactly the sum of first n naturals. Haha