I found something, but I'm not sure what it is. Summation Notation
Triple summation equation with two variable upper limits. The variable has a positive integer domain - YouTube
amsmath - Using a primed sum operator in display and text mode - TeX - LaTeX Stack Exchange
subscripts - Having sub/super scripts on the side for \sum - TeX - LaTeX Stack Exchange
math mode - making a big summation sign - TeX - LaTeX Stack Exchange
How do you use summation(∑) in LaTeX? | Sigma symbol
Positioning limits above and below a summation in LaTeX/Overleaf - YouTube
How do you use summation(∑) in LaTeX? | Sigma symbol
math mode - Making the subscript under the summation - TeX - LaTeX Stack Exchange
math mode - Different Sum signs - TeX - LaTeX Stack Exchange
sum and \prod math symbol are not displayed · Issue #4 · SEGTeX/texmf · GitHub
r - Double Variable Summation - Stack Overflow
math mode - making a big summation sign - TeX - LaTeX Stack Exchange
File:Latex math example substack sum.png - Wikimedia Commons
How to write Sigma(∑,σ) symbol in LaTeX?
How do you use summation(∑) in LaTeX? | Sigma symbol
How do you use summation(∑) in LaTeX? | Sigma symbol
math mode - Alternative sum symbol for Neo Euler - TeX - LaTeX Stack Exchange
math operators - LaTeX adjusting \sum limits - TeX - LaTeX Stack Exchange
Hints for finding the formula for the finite summation of a polynomial : r/calculus
How to Create and use summation symbol in LaTeX
2,024 Summation Images, Stock Photos, 3D objects, & Vectors | Shutterstock
Vertical Stacking in Series Notation Using LaTeX Fractions - αlphαrithms
7.2 "Sigma notation" for sums - YouTube
