Proof Tree Rendering in HTML

Here comes a proof tree: \begin{prooftree} \AXC{$1 + 2$} \AXC{$1 + 2 + 3$} \BIC{$1 + 2$} \AXC{$1 + 2 + 3$} \RightLabel{Label} \BIC{$1 + 2 + 3 + 4$} \end{prooftree}