#Mathematica 83 49 43 54 51
Mathematica 83 49 43 54 51
Print@@#&/@(Sum[k~DiamondMatrix~17,{k,0,8}]/.0->" ")

With 3 bytes saved thanks to Kelly Lowder.
Analysis
The principal part of the code, Sum[DiamondMatrix[k, 17], {k, 0, 8}], can be checked on WolframAlpha.
The following shows the underlying logic of the approach, on a smaller scale.
a = 0~DiamondMatrix~5;
b = 1~DiamondMatrix~5;
c = 2~DiamondMatrix~5;
d = a + b + c;
e = d /. 0 -> "";
Grid /@ {a, b, c, d, e}
