Let $F$ is an $n$-ary relation (with $n$ being any index set).
Can the following formula be simplified? $(\lambda x\in n:s(x))\in F$ ($s$ is some function).
Here $\lambda$ is defined as: $(\lambda x\in D:f(x)) = \{(x;f(x)) | x\in D\}$ for every set $D$ and formula $f(x)$ dependent on a variable $x$.