There is a column of numbers: 1 / 2.. - 2 / 5.. 3 / 10.. - 4 / 17.. then the seventh number is | Math enthusiast | Mathematical art

There is a column of numbers: 1 / 2.. - 2 / 5.. 3 / 10.. - 4 / 17.. then the seventh number is

First, the first is positive, the second is negative, and so on, the seventh should be positive
The observation molecule is 1, 2, 3, 4. So the seventh one should be 7
2 + 3 is 5, 5 + 5 is 10, 10 + 7 is 17, so the number added is 3, 5, 7, 9, 11, 13
So the seventh number is 7 out of 50

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