A semi-coprime array (SCA) interleaves two undersampled uniform linear arrays (ULAs) and a Q-element standard ULA. The undersampling factors of the first two arrays are QM and QN, respectively, where M and N are coprime. The resulting non-ULA is highly sparse. Taking the minimum of the absolute values of the conventional beampatterns of the three arrays results in a beampattern that is free of grating lobes. A SCA requires fewer sensors than other popular sparse arrays such as coprime arrays, nested arrays, and minimum redundant arrays for a given aperture. Also, a SCA exhibits better side lobe patterns than other sparse arrays. This means that a SCA is better able to mask signals away from the look direction and detect weak sources in the presence of strong interferers. In this paper, the author explores the direction of arrival estimation with the SCA. The results illustrate the SCA's ability to reduce the number of sensors and decrease system cost and complexity in various signal processing applications.