把al=1代入2sn=2pan^2+pan-p,得2s1=2pa1^2+pa1-p所以解得p=1所以2sn=2an^2+an-1然后你把(n-1)项时的代入得2sn-1=2an-1^2+an-1-1再用上式减下式整理后可得an-an-1=1/2,显然是等差数列,得an=n/2+1/2手机党打字不容易,采纳吧
