Is the following inequality correct? 5 1 1 + 5 2 1 + 5 3 1 + ⋯ 2 0 0 1 > 1
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5 1 1 + 5 2 1 + 5 3 1 + ⋯ + 2 0 0 1
Note that n < n + 1 < n + 2 < ⋯ n + k ⟹ n 1 > n + 1 1 + n + 2 1 > ⋯ > n + k 1 for n ∈ N and k = 1 , 2 , 3 , ⋯ S = 5 1 1 + 5 2 1 + 5 3 1 + ⋯ + 2 0 0 1 = ( 5 1 1 > 1 0 0 1 + 5 2 1 > 1 0 0 1 + 5 3 1 > 1 0 0 1 ⋯ + 9 9 1 > 1 0 0 1 + 1 0 0 1 ) + ( 1 0 1 1 > 2 0 0 1 + 1 0 2 1 > 2 0 0 1 + 1 0 3 1 > 2 0 0 1 + ⋯ + 2 0 0 1 ) = n = 5 1 ∑ 1 0 0 n 1 > 5 0 × 1 0 0 1 + k = 1 0 1 ∑ 2 0 0 k 1 > 1 0 0 × 2 0 0 1 > 2 1 + 2 1 > 1 Thus the answer is yes .
Noting that k = 5 1 ∑ 1 0 0 k 1 > 5 0 × 1 0 0 1 = 2 1 , k = 1 0 1 ∑ 1 5 0 k 1 > 5 0 × 1 5 0 1 = 3 1 and k = 1 5 1 ∑ 2 0 0 k 1 > 5 0 × 2 0 0 1 = 4 1 ,
we find that k = 5 1 ∑ 2 0 0 k 1 = k = 5 1 ∑ 1 0 0 k 1 + k = 1 0 1 ∑ 1 5 0 k 1 + k = 1 5 1 ∑ 2 0 0 k 1 > 2 1 + 3 1 + 4 1 = 1 2 6 + 4 + 3 = 1 2 1 3 > 1 . The answer is therefore yes .
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We form the summations k = 5 1 ∑ 2 0 0 k 1 = k = 5 1 ∑ 1 0 0 k 1 + k = 1 0 1 ∑ 1 5 0 k 1 + k = 1 5 1 ∑ 2 0 0 k 1 > 2 1 + 3 1 + 4 1 = 1 2 6 + 4 + 3 = 1 2 1 3 > 1 .
So 5 1 1 + 5 2 1 + 5 3 1 + ⋯ 2 0 0 1 > 1 is greater than 1