Squarefree Hilbert number
= Squarefree Hilbert number
In the multiplicative set of <Hilbert numbers>, a squarefree Hilbert number is one divisible by no square $h^2$ of a <Hilbert number> $h>1$. This is weaker than being a <squarefree integer>: $9$ is a squarefree Hilbert number because its square divisor $9=3^2$ has $3$ outside the <Hilbert numbers>.