What does Sequence[2,4]^2 mean?

Question

I am learning pattern matching. An example that confuse me is as follows.

Foo[x__?EvenQ] := x^2;
Foo[2, 4]

which is equal to Sequence[2,4]^2 which in turns equal to 65536.

What does it mean? Why is it 65536? I really don't understand what kind of algorithm is applied here.

Answer 1

Switching away from infix notation might make things more clear:

Sequence[2, 4]^2 === Power[Sequence[2, 4], 2] === Power[2, 4, 2]

According to the documentation of Power:

and so we have

Power[2, 4, 2] == 2^(4^2) == 65536