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#7f480b0b-daae-4c40-bdd7-27b15a14e7d5中等填空题二项式定理计数原理

10.已知SnS_{n}是数列{an}\{a_{n}\}的前nn项和,若(12x)2021=b0+b1x+b2x2++b2021x2021(1-2x)^{2021}=b_{0}+b_{1}x+b_{2}x^{2}+\ldots +b_{2021}x^{2021},数列{an}\{a_{n}\}的首项a1=b12+b222++b202122021a_{1}=\frac{b_1}{2}+\frac{b_2}{2^2}+\ldots +\frac{b_{2021}}{2^{2021}}an+1=SnSn+1a_{n+1}=S_{n}\centerdot S_{n+1},则S2021=(S_{2021}=(  ))