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已知数列{an}满足a1=1,a2=2,an+2=,则该数列的前20项的和为_______...
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已知数列{a
n}满足a
1=1,a
2=2,a
n+2=
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAJQAAAAjCAYAAABy8yMZAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
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Mhefg2zssxH9N8p27bkUcwcjm/Jk6ru9fno4ff+ToRyt2dRABRNWuPITKAPNztERMG1MOC8BnQCG
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gH2qeskDDVwIAtx1xKLYdTnzL5bgmIDYjrbdB71maEfM0xa0mANKg+LHjmEyhSjmFphVc6sOylNp
ccOS582sAKDYdS9Fd6u54TJT0+WaZ2DiAu0wgbDQ8GD8X/nnAqh037VNlOh9Skmdt8HtF3PLTSt9
Il02cIp98ews11wue1Mli3MtDjyTf8QEX2+JWuYeLCs5WeBnb0AXYZMLVU4T7PVM301fnDguW8zF
Nu3eV6iZLWwWFMdq7Pr5M+7BMgMAKiVrCLZ/3ulGAyo0y2+9NNp0l8fTB8uurMxlqaneGQ/jnGaY
7ERpjWZwcxgQeRcUBtmBKEKmdxAwdunjIaYtRJuYt/7sHoT9jzm+UipyOyyIFuUmLGG7XlpFm1+v
8iPMxN6C0eydQH3JE6uEwyQSk8diSM1eCJRzShM7Navu88otLYXPqvZ7PoTX7HVAfe3QnAfQ74qy
7WCVaPYqoIJTiogKde1w+ACZettsMVSpZq8BKr6731goraVtkudqNHsNUJOM4fRmLqCmH8J7dWAB
da/xmN6aBdT0Q3ivDvwDZeCu5AukM58AAAAASUVORK5CYII=
)
,则该数列的前20项的和为________.
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