WW

<< Combinatorica
A = {1, 2, 3, 4, 5};
ProdCart = CartesianProduct[A, A];
H = {};
For[i = 1, i <= Length[ProdCart], i++,
       L = ProdCart[[i]];
      If[ (L[[1]] - L[[2]])^2 == ProdCart[[i]], H = Append[H, L]];
   ];

Subscript[M, R] = ConstantArray[0, {Length[A], Length[A]}];
For[i = 1, i <= Length[A], i++,
 For[j = 1, j <= Length[A], j++,
       If[ MemberQ[H, {A[[i]], A[[j]] } ] == True,

   Subscript[M, R] = ReplacePart[Subscript[M, R], 1, {i, j}];
         ]
      ]
  ]
AdjacencyGraph[Subscript[M, R], VertexLabels -> "Name",
 ImagePadding -> 10, DirectedEdges -> True]
Print["\!\(\*SubscriptBox[\(M\), \(R\)]\) = " MatrixForm[Subscript[M,
   R]]]