Abbreviation: ISRng$_0$
An \emph{idempotent semiring with zero} is a semirings with zero $\mathbf{S}=\langle S,\vee,0,\cdot \rangle $ such that $\vee$ is idempotent: $x\vee x=x$
Let $\mathbf{S}$ and $\mathbf{T}$ be idempotent semirings with zero. A morphism from $\mathbf{S}$ to $\mathbf{T}$ is a function $h:S\rightarrow T$ that is a homomorphism:
$h(x\vee y)=h(x)\vee h(y)$, $h(x\cdot y)=h(x)\cdot h(y)$, $h(0)=0$
Example 1:
$\begin{array}{lr}
f(1)= &1
f(2)= &2
f(3)= &12
f(4)= &129
f(5)= &1852
f(6)= &
\end{array}$