Let ar∈{i1,…,ik}∩{a1,…,ak}. Thus ar=is for some s=r. Now there are two cases: Case 1. as∈{i1,…,ik}. Let as=it. In this case a derangement x=(x1,…,xn) satisfies the condition xij=aj if and only if the derangement x′=(x1′,…,xit−1′,xit+1′,xn′) of the set [n]\{it} satisfies the condition xij′=aj′ for all j=t, where aj′=aj for j=s and as′=at. This provides a one to one correspondence between the derangements x=(x1,…,xn) of [n] with xij=aj for the given sets \left\{i_{1}, \ldots, i_{k}\right\}and{a1,…,ak} with ℓ elements in their intersections, and the derangements x′=(x1′,…,xit−1′,xit+1′,xn′) of [n]\{it} with xij=aj′ for the given sets \left\{i_{1}, \ldots, i_{k}\right\} \backslash\left\{i_{t}\right\}and{a1′,…,ak′}\{at′} with ℓ−1 elements in their intersections. Case 2. as∈/{i1,…,ik}. In this case a derangement x=(x1,…,xn) satisfies the condition xij=aj if and only if the derangement x′=(x1′,…,xas−1′,xas+1′,xn′) of the set [n]\{as} satisfies the condition xij′=aj for all j=s. This provides a one to one correspondence between the derangements x=(x1,…,xn) of [n] with xij=aj for the given sets \left\{i_{1}, \ldots, i_{k}\right\}and{a1,…,ak} with ℓ elements in their intersections, and the derangements x′=(x1′,…,xas−1′,xas+1′,xn′) of [n]\{as} with xij=aj for the given sets \left\{i_{1}, \ldots, i_{k}\right\} \backslash\left\{i_{s}\right\}and{a1,…,ak}\{as} with ℓ−1 elements in their intersections. These considerations show that Δ(n,k,ℓ)=Δ(n−1,k−1,ℓ−1). Iterating this argument we have Δ(n,k,ℓ)=Δ(n−ℓ,k−ℓ,0) We can therefore assume that ℓ=0. We thus evaluate Δ(n,k,0), where 2k⩽n. For k=0, we obviously have Δ(n,0,0)=Dn. For k⩾1, we claim that Δ(n,k,0)=Δ(n−1,k−1,0)+Δ(n−2,k−1,0) For a derangement x=(x1,…,xn) satisfying xij=aj there are two cases: xa1=i1 or xa1=i1. If the first case occurs then we have to evaluate the number of derangements of the set [n]\{i1,a1} for the given sets \left\{i_{2}, \ldots, i_{k}\right\}and{a2,…,ak} with 0 elements in their intersections. The number is equal to Δ(n−2,k−1,0). If the second case occurs then we have to evaluate the number of derangements of the set [n]\{a1} for the given sets \left\{i_{2}, \ldots, i_{k}\right\}and{a2,…,ak} with 0 elements in their intersections. The number is equal to Δ(n−1,k−1,0). We now use induction on k to show that Δ(n,k,0)=i=0∑k−1(ik−1)n−(k+i)D(n+1)−(k+i),2⩽2k⩽n For k=1 we have Δ(n,1,0)=Δ(n−1,0,0)+Δ(n−2,0,0)=Dn−1+Dn−2=n−1Dn Now let the result be true for k−1. We can write Δ(n,k,0)=======Δ(n−1,k−1,0)+Δ(n−2,k−1,0)i=0∑k−2(ik−2)(n−1)−(k−1+i)Dn−(k−1+i)+i=0∑k−2(ik−2)(n−2)−(k−1+i)D(n−1)−(k−1+i)i=0∑k−2(ik−2)n−(k+i)D(n+1)−(k+i)+i=1∑k−1(i−1k−2)(n−1)−(k+i−1)Dn−(k+i−1)n−kD(n+1)−k+i=1∑k−2(ik−2)n−(k+i)D(n+1)−(k+i)+n−(2k−1)D(n+1)−(2k−1)+i=1∑k−2(i−1k−2)n−(k+i)D(n+1)−(k+i)n−kD(n+1)−k+i=1∑k−2[(ik−2)+(i−1k−2)]n−(k+i)D(n+1)−(k+i)+n−(2k−1)D(n+1)−(2k−1)n−kD(n+1)−k+i=1∑k−2(ik−1)n−(k+i)D(n+1)−(k+i)+n−(2k−1)D(n+1)−(2k−1)i=0∑k−1(ik−1)n−(k+i)D(n+1)−(k+i).