I think I have found a winner for (Asian) Indians: Cupertino, Santa Clara County, CA: 21.4% Indian, 5,179.6 ppl per sq mi.
Depends on the size of the area. Parts of western Nassau County have denser areas with high Asian Indian populations, but they are villages/ hamlets very small in size
New Hyde Park, NY 16.7% Asian Indian , 11,281.8 ppl per sq mi, population 9,712
Bellerose Terace, NY 11.7% Asian Indian , 22,212 per sq mi, but population only 2,198
Herricks, NY 23.2% Asian Indian- 7,158 ppl per sq mi, population 4,295
