CREATE TABLE table_name_18 (masculine_an_stems VARCHAR(255), feminine_ō_stems VARCHAR(255), masculine_u_stems VARCHAR(255))
What is the an-stem for the word which has an ö-stems of siangar and an u-stem ending of syni?
    
SQL: SELECT masculine_an_stems FROM table_name_18 WHERE feminine_ō_stems = "siangar" AND masculine_u_stems = "syni"