JERUSALEM — Seven Israeli teenagers were in custody on Monday, accused of what a police official and several witnesses described as an attempted lynching [1] of several Palestinian [2] youths, laying bare the undercurrent of tension in this ethnically mixed but politically divided city. A 15-year-old suspect standing outside court said, “For my part he can die, he’s an Arab.” The police said that scores of Jewish youths were involved in the attack late Thursday in West Jerusalem’s Zion Square, leaving one 17-year-old unconscious and hospitalized. Hundreds of bystanders watched the mob beating, the police said — and no one intervened.