I have a pyramid which has 5 vertex and 18 indices. As I want to add normals to each face I just found solution for normals for each vertex. That means I can't use indices to define my pyramid I need to have 18 vertex (and 3 times the same vertex for the same point in space).

There must be a solution to use normals not on vertex base but on index base.

Some code (javascript):

var vertices = [
    -half, -half,  half, // 0 front left
     half, -half,  half, // 1 front right
     half, -half, -half, // 2 back right
    -half, -half, -half, // 3 back left
      0.0,  Math.sqrt((size * size) - (2 * (half * half))) - half,   0.0  // 4 top
];

var vertexNormals = [
    // front face
     normaleFront[0],  normaleFront[1],  normaleFront[2],
     normaleFront[0],  normaleFront[1],  normaleFront[2],
     normaleFront[0],  normaleFront[1],  normaleFront[2],

    // back face
     normaleBack[0],  normaleBack[1],  normaleBack[2],
     normaleBack[0],  normaleBack[1],  normaleBack[2],
     normaleBack[0],  normaleBack[1],  normaleBack[2],

    // left face
     normaleLeft[0],  normaleLeft[1],  normaleLeft[2],
     normaleLeft[0],  normaleLeft[1],  normaleLeft[2],
     normaleLeft[0],  normaleLeft[1],  normaleLeft[2],

    // right face
     normaleRight[0],  normaleRight[1],  normaleRight[2],
     normaleRight[0],  normaleRight[1],  normaleRight[2],
     normaleRight[0],  normaleRight[1],  normaleRight[2],

    // bottom face
     0.0, -1.0, 0.0,
     0.0, -1.0, 0.0,
     0.0, -1.0, 0.0,
     0.0, -1.0, 0.0,
     0.0, -1.0, 0.0,
     0.0, -1.0, 0.0,
];

var pyramidVertexIndices = [
    0, 1, 4, // Front face
    2, 3, 4, // Back face
    3, 0, 4, // Left face
    1, 2, 4, // Right face
    0, 1, 2,   2, 3, 0, // Bottom face
];