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

what is the pearson symbol for the formula with the lightest density ?
SELECT "formula" FROM table_203_613 ORDER BY "density, g/cm3" LIMIT 1
SELECT "formula" FROM "table_203_613" ORDER BY "density, g/cm3" FETCH FIRST 1 ROWS ONLY