beta-D-Galp-(1->4)-beta-D-GlcpNAc-(1->3)-[3)-beta-D-Galp-(1->4)-beta-D-GlcpNAc-(1->]n[beta-D-Galp-(1->4)-beta-D-GlcpNAc-(1->6)]-beta-D-Galp-(1->4)-beta-D-GlcpNAc(1->