After experimenting with polynomial expansions for the Riemann $\Xi(t)=\xi\left(\frac12+it\right)$-function, I landed on these two equations:
with $M$ the KummerM confluent hypergeometric funcion and $L$ the generalised Laguerre polynomial.
Both equations are equal except for the square in the parameter of $\Xi(x)$.
Question (probably far fetched):
Could it be possible to derive some relation between $\Xi(x^2)$ and $\Xi(x)$ from these equations?
P.S. A similar set of equations exists for $\Xi(1)$.
