3＋5＋7＋9… ＋（2n－1）＋（2n＋1）＝

1/3+1/(3+3)+1/(3+3+5)+1/(3+3+5+7)+1/(3+3+5+7+9)+.+1/(3+3+5+7+.+2n-1)

Step 1: the nth term equals 1 / (3 + (2n-1)) * ((2n-1-3) / 2-1) / 2 = 1 / (n ^ 2 + 2)
Step 2:1/(n^2+2) < 1/ (n^2-1)
Step 3:1/ (n^2-1)

What is the value of 1 + 3 + 5 + 7 + 9 +. + 2n-3 + 2N-1

There are n numbers in total, using Gauss formula: (first term + last term) * number of terms / 2, 1 + 3 + 5 + 7 + 9 +. + 2n-3 + 2N-1 = (1 + 2n-1) xn / 2 = n ^ 2

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