We consider the problem
Δ2u = K(y)|u|8∕(n−4)u in ℝn with u,Δu → 0 as |y|→∞, where K is a bounded and
continuous function on ℝn, n ≥ 5. Our aim is to construct infinitely many solutions
which concentrate around k points, k ≥ 2, under some appropriate conditions on
K. Moreover we prove that there is no solution which concentrates at one
point.