GHZ preparation with Hadamard and controlled-Z gates ($(|0{⟩}^{\otimes n}+|1{⟩}^{\otimes n})/\sqrt{2}$)

For $n\ge 2$, apply a Hadamard gate to one qubit, then controlled-NOTs from it to all others. Replacing each controlled-NOT gate by a target Hadamard, a Controlled-Z gate, and another target Hadamard uses $1+3(n-1)$ allowed gates. Each one-qubit reduced state is $I/2$, proving entanglement across each qubit-versus-rest bipartition.