Generating centered hexagonal lattice

Question

I want to create a hexagonal lattice but it should be centered basically the whole lattice is a central hexagon and then layers of hexagon around, like shown in the figure. (may be my description is confusion, but right now that is how I am seeing it).

So I want to generate the coordinates for lattice below. I found many algorithm to create square lattice of hexagons but I want to ask if there is a algorithm for following lattice too.

Answer 1

Note:

N-th layer consists of 6N cells.

First cell of that layer in your representation has coordinate shift

(N*A*Sqrt(3)/2, N*A*3/2), where A is edge length.

First cell of that layer has number

2+3*N*(N-1)                     //(you have missed 14)  

You can start from the first cell of Nth layer, make N more cells to left, N cells to left-down and so on...