由公差为d的等差数列{an}依次相邻两项之和:a1+a2,a2+a3,a3+a4,a4+a5,...,an+(an+1)

拿个简单的例子,比如2,4,6,8,10 d=2
则2 4=6,4 6=10 6 8=14,8 10=18,很容易就能看得出来,a1 a2,a2 a3,a4 a5,……那么新组成的数列就为2d
则可得an'=a1 a2 (2d)(n'-1)