Justin Timberlake’s ‘SexyBack’ held the No. 1 title on the Billboard Hot 100 singles chart for a second week Thursday. Black Eyed Peas singer Fergie’s ‘London Bridge’ was steady at No. 2, Gnarls Barkley’s ‘Crazy’ climbed one to No. 3, and the Pussycat Dolls’ ‘Buttons’ featuring Snoop Dogg rose one to No. 4.