A Sheffer sequence for is called the associated sequence for , and a sequence of polynomials satisfying the orthogonality conditions

where is the delta function, is said to be associated to .

A Sheffer sequence for is called the associated sequence for , and a sequence of polynomials satisfying the orthogonality conditions

where is the delta function, is said to be associated to .

Weisstein, Eric W. "Associated Sequence."
From *MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/AssociatedSequence.html