Riordan array

A Riordan array is an infinite lower triangular matrix, $D$, constructed out of two formal power series, $d(t)$ and $h(t)$, in such a way that $d_{n,k} = [t^n]d(t)\left(t h(t)\right)^k$.

References

• Sprugnoli, Renzo, An Introduction to Mathematical Methods in Combinatorics (PDF)