CREATE TABLE table_203_613 (id DECIMAL, "formula" TEXT, "color" TEXT, "symmetry" TEXT, "space group" TEXT, "no" DECIMAL, "pearson symbol" TEXT, "a  ( pm ) " DECIMAL, "b  ( pm ) " DECIMAL, "c  ( pm ) " DECIMAL, "z" DECIMAL, "density ,  g/cm3" DECIMAL)

of those listed , which compound has the highest density ?
SELECT "formula" FROM table_203_613 ORDER BY "density, g/cm3" DESC LIMIT 1
SELECT "formula" FROM "table_203_613" ORDER BY "density, g/cm3" DESC NULLS LAST LIMIT 1