Sequence - 1,3, - 2, - 4,11, () | Math enthusiast | Mathematical art

Sequence - 1,3, - 2, - 4,11, ()

-1*3+1=-2
3*(-2)+2=-4
(-2)*(-4)+3=11
-4*11+4=-40

Find the sequence 11 + 2, 11 + 2 + 3 ，11+2+… +The sum of the first n terms of (n + 1)

∵11+2+… +(n + 1) = 1 (n + 1) (n + 2) 2 = 2 (n + 1) (n + 2) = 2 (1n + 1 − 1n + 2), ‖ sequence 11 + 2, 11 + 2 + 3 ，11+2+… +The sum of the first n terms of (n + 1) is: SN = 2 (12 − 13 + 13 − 14 +...) +1n+1−1n+2）=2（12−1n+2）=nn+2．

Number sequence: what is the 20th number of 1,3,2,4,3,5

He is an even number
According to the arithmetic sequence with 3 as the first term and 1 as the tolerance, the twentieth number is 12

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