# Sequence there !

Algebra Level 3

What is the sum of first 25 terms of the sequence where $$n^{th}$$ term is defined by the formula

$$a_n = n^2 -2n -1$$

Details and assumptions

Sequence starts with $$a_1$$ , and it has a value $$a_1 = 1-2-1=-2$$

$$a_2 = 2^2-2\times 2 -1 = -1$$

$$a_3 = 3^2 - 3\times 2 -1 = 2$$

$$a_4 = 4^2-4\times 2 -1 =7$$ . . . .

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