According to Katy Perry, California Gurls is an answer song to what song by Jay-Z that featured vocals by Alicia Keys?
California Gurls:  According to Perry, "California Gurls" is an answer song to "Empire State of Mind" (2009), by Jay-Z and Alicia Keys. Empire State of Mind: "Empire State of Mind" is a song performed by American rapper Jay-Z and featuring vocals by American singer Alicia Keys that was written by Angela Hunte and Jane't Sewell-Ulepic.
Empire State of Mind