code: public static long[] getNumbers(IAtomContainer atomContainer) throws CDKException {
          String aux = auxInfo(atomContainer);
          long[] numbers = new long[atomContainer.getAtomCount()];
          parseAuxInfo(aux, numbers);
          return numbers;
      }
docs: Makes an array containing the InChI atom numbers of the non-hydrogen
  atoms in the atomContainer. It returns zero for all hydrogens.
  
  @param  atomContainer  The {@link IAtomContainer} to analyze.
  @return                The number from 1 to the number of heavy atoms.
  @throws CDKException   When the InChI could not be generated