The number k of "internal" layers for the lamellar self-assembled state of a new class of multiblock copolymers A-b-(B-b-C)(m)-b-B-b-A is determined as a function of m in the strong segregation limit. Here the outer A-blocks are assumed to be considerably longer than the m + 1 blocks of equal length of the (B-b-C)(m)-b-B middle multiblock, and the self-assembled state is assumed to consist of k "thin" B- and C-layers sandwiched between "thick" A-layers. The predictions are in excellent agreement with the available experimental data.