找规律 7,13,39,61,103,( )

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找规律7,13,39,61,103,()找规律7,13,39,61,103,()找规律7,13,39,61,103,()an=(2n)²+3(-1)^(n+1)a6=12²-3=1

找规律 7,13,39,61,103,( )
找规律 7,13,39,61,103,( )

找规律 7,13,39,61,103,( )
an = (2n)² + 3(-1)^(n+1)
a6 = 12² - 3
= 144 - 3
= 141

7,13,39,61,103,(141 )
an=4n^2+3*(-1)^(n+1)

4+3,16-3,36+3,64-3,100+3,12^2-3
括号里填12^2-3=144-3=141