Curious variadic non-type template parameter pattern

Question

I have working 'compile-time' code where a curious pattern keeps occuring. The simplest case is:

    template <int... E>
    struct SomeInts { };

    template <int... E>
    constexpr auto InvertF( const SomeInts<E...>& ) -> SomeInts<( -E )...>;

    template <typename S>
    using Invert = decltype( InvertF( S() ) );

    // use case:
    using X = Invert<SomeInts<1, 3, 3, 7>>;  // => SomeInts<-1, -3, -3, -7>

Straightforward enough. The detour via the function-template InvertF looks somewhat clever. I've never seen this before, so it's either genius or superfluous!

Can this be simplified? How?

Just my thoughts: If the using Invert template could extract an E... pack somehow, it could just be = SomeInts<(-E)...>. Smells like template template parameter, but I just can't get my head around this. The standard is probably to have a struct instead of using, but the matching/extraction issue remains.