  The hierarchy of conformally invariant k-th powers of the Laplacian acting on
a scalar field with scaling dimensions $\Delta_{(k)}=k-d/2$, k=1,2,3 as
obtained in the recent work [1] is rederived using the Fefferman-Graham d+2
dimensional ambient space approach. The corresponding mysterious "holographic"
structure of these operators is clarified. We explore also the d+2 dimensional
ambient space origin of the Ricci gauging procedure proposed by A. Iorio, L.
O'Raifeartaigh, I. Sachs and C. Wiesendanger as another method of constructing
the Weyl invariant Lagrangians. The corresponding \emph{gauged} ambient metric,
Fefferman-Graham expansion and extended Penrose-Brown-Henneaux transformations
are proposed and analyzed.
