Help getting vertex indices from a grid

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I'm folloing this little tutorial on how to get indices from a grid to build a GL_TRIANGLE_STRIP mesh <a href="http://dan.lecocq.us/wordpress/2009/12/25/triangle-strip-for-grids-a-construction/" rel="nofollow">http://dan.lecocq.us/wordpress/2009/12/25/triangle-strip-for-grids-a-construction/</a>

I'm getting some of the indices in the right order but I can't workout the logic on vertices 7 and 8 as he shows in the last figure

Here is my code:

cols = 4;
rows = 4;

sizeW = 320.0f;
sizeH = 240.0f;

float spaceX = sizeW / cols;
float spaceY = sizeH / rows;

// Mesh indices
for ( int x = 0; x < cols-1; x++ ) {
    for ( int y = 0; y < rows-1; y++ ) {
        int i = y + x * rows;

        cout << "{a, b, c}: " << i << ", " << i+4 << ", " << (i+4)-3;
        cout << endl;
    }
    cout << "------------" << endl;
}
vboMesh.setMesh( mesh, GL_DYNAMIC_DRAW );

cout << "mesh number of vertices: " << mesh.getNumVertices() << endl;

And here is my output:

0, 4, 1
1, 5, 2
2, 6, 3
--------
4, 8, 5
5, 9, 6
6, 10, 7
--------
8, 12, 9
9, 13, 10
10, 14, 11

<strong>UPDATE:</strong>
Following the comments, I workout another algorithm to get the indices, this is what I have so far:

// Mesh indices
int totalQuads  = (cols-1) * (rows-1);
int totalTriangles  = totalQuads * 2;
int totalIndices    = (cols*2) * (rows-1);
cout << "total number of quads: " << totalQuads << endl;
cout << "total number of triangles: " << totalTriangles << endl;
cout << "total number of indices: " << totalIndices << endl;

int n = 0;
int ind = 0;
vector<int> indices;
for ( int i = 0; i < totalIndices; i++ ) {
    //cout << i % (cols*2) << ", ";
    ind = i % (cols*2);
    if ( i % (cols*2) == 0 ) {
        n++;
        cout << n << endl;

        if ( n%2 == 1 ) {
            cout << "forward" << endl;
        }
        else {
            cout << "backward" << endl;
        }
    }

    indices.push_back( ind );
}
//cout << endl;

This code tells me when I need to go forward and when I need to go backward, by doing <strong>i % (cols*2)</strong> I get a list like 0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, so in theory all I need to do now is +4 -3 going forward and +4 -5 going backward

<strong>UPDATE 2:</strong>
Made some progress, these are the new results
0, 4, 1, 5, 2, 6, 3, 7, 7, 11, 6, 10, 5, 9, 4, 8, <strong>14, 18, 15, 19, 16, 20, 17, 21</strong> the last set of numbers is still wrong

// Mesh indices
int totalQuads      = (cols-1) * (rows-1);
int totalTriangles  = totalQuads * 2;
int totalIndices    = (cols*2) * (rows-1);
cout << "total number of quads: " << totalQuads << endl;
cout << "total number of triangles: " << totalTriangles << endl;
cout << "total number of indices: " << totalIndices << endl;

bool isGoingBackwards = false;
int n = 0;
int ind = 0;
vector<int> indices;

for ( int i = 0; i < totalIndices; i++ ) {
    if ( i % (cols*2) == 0 ) {
        ind++;
        if ( ind%2 == 1 ) {
        n = ((cols*2) - 1) * (ind-1);
            cout << "forward " << n << endl;
        isGoingBackwards = false;
        }
        else {
            n = ((cols*2) - 1) * (ind-1);
        cout << "backward " << n << endl;
        isGoingBackwards = true;
        }
    }

    indices.push_back( n );


    if ( i%2 == 0 ) {
        n += 4;
    }
    else {
        ( isGoingBackwards ) ? n -= 5 : n -= 3;
    }
}

<strong>UPDATE 3:</strong>

I finally got it! here is the new code

int n   = 0;
int colSteps = cols * 2;
int rowSteps = rows - 1;
vector<int> indices;
for ( int r = 0; r < rowSteps; r++ ) {
    for ( int c = 0; c < colSteps; c++ ) {
        int t = c + r * colSteps;

        if ( c == colSteps - 1 ) {
            indices.push_back( n );
        }
        else {
            indices.push_back( n );

            if ( t%2 == 0 ) {
                n += cols;
            }
            else {
                (r%2 == 0) ? n -= (cols-1) : n -= (cols+1);
            }
        }
    }
}