1.若n=4时,则原数列为a1,a2,a3,a4.
⑴若删去a1,
则a3∧2=a2×a4,
→d=0,
矛盾
⑵若删去a2,
→a5=0
⑶若删去a3
→a1=d
→a1/d=1
⑷若删去a4
→d=0
综上所述,a1/d=0