>>... It does not create an n

>>... It does not create an n X n array

I agree and it looks like a typing error. If Yes it should look like:

...
double *a = new double[ n * n ];
call_dsyrdb( a, &n );
delete [] a;
...

and if initialization for the 2-D array a is needed it could be done as follows:

...
double *a = new( 0.0L ) double[ n * n ];
call_dsyrdb( a, &n );
delete [] a;
...