A core for an acoustic attenuation panel extending between a first and a second end face, the core including a plurality of tubular polygonal cells having a main axis of extension between the end faces, each cell including an internal cavity delimited by lateral walls extending between the first and second end faces and opening out into each of the two end faces, the cells being expandable in a direction parallel to the end faces, each polygonal cell having septa extending transversely relative to the main axis and being offset there along, wherein each septum is folded in a W-shape at least between one of the lateral walls and another of the lateral walls and has a through orifice, the orifices of two consecutive septa being offset radially with respect to the main axis to form a baffle.