等比数列an的前n项和为Sn,且4a1,2a2,a3成等差数列.若a1等于1,则S4为多少?

问题描述:

等比数列an的前n项和为Sn,且4a1,2a2,a3成等差数列.若a1等于1,则S4为多少?

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