... + 2n - 2 = 1 + 2(n-1) The sequence { an } = 1, 3, 5, 7, 9, ..... is an arithmetic sequence with a1 = 1 and d = 2. The 6th to 10th terms of this arithmetic progression are a6 = 1 + 2(6-1) = 1 + 10 = 11 a7 = 1 + 2(7-1) = 1 + 12 = 13 a8 = 1 + 2(8-1) = 1 + 14 = 15 a9 = 1 + 2(9-1) = 1 + 16 = 17 a10 = 1 + 2(10-1) = 1 + 18 = 19 The sum of the first n terms of the sequence { an } = 1, 3, 5, 7, 9,. . . is Sn = n (2(1) + (n - 1)2) / 2 = n (2 + 2n - 2) / 2 = 2n2 / 2 = n2 We can verify this for the first 5 terms: S1 = 12 = 1 S2 = 22 ...

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