在数列{an}中,若a2n−a2n−1=p(n≥2,n∈Z∗,p为常数),则称{an}为“等方差数列”,下列是对“等方差数列”的判断;①若{an}是等方差数列,则{a2n}是等差数列;②{(−1)n}是等方差数列;③若{an}是等方差数列,