Abstract

We prove that the system of difference equations xn+1(i)=λixn(i)+fi(αixn(i+1)βixn1(i+1)), i{1,2,,k}, n, (we regard that xn(k+1)=xn(1)) is permanent, provided that αiβi, λi+1[0,βi/αi), i{1,2,,k}, fi:, i{1,2,,k}, are nondecreasing functions bounded from below and such that there are δi(0,1) and M>0 such that fi(αix)δix, i{1,2,,k}, for all xM. This result considerably extends the results existing in the literature. The above system is an extension of a two-dimensional discrete neural network system.