Evaluate: m → ∞ lim ( ( n = 1 ∑ m n 1 k = 1 ∑ n − 1 k ( − 1 ) k ) + lo g ( 2 ) H m )
The answer is of the form: B π A − C ( lo g C ) D for positive integers A , B , C , D .
Find A + B + C + D .
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We see that n = 1 ∑ m n 1 ( k = 1 ∑ n − 1 k ( − 1 ) k ) − ln ( 2 ) H m = = = n = 1 ∑ m n 1 ( k = 1 ∑ n − 1 k ( − 1 ) k − ln 2 ) n = 1 ∑ m n 1 ( k = n ∑ ∞ k ( − 1 ) k − 1 ) = k = 1 ∑ ∞ k ( − 1 ) k − 1 ⎝ ⎛ n = 1 ∑ m i n ( k , m ) n 1 ⎠ ⎞ k = 1 ∑ m k ( − 1 ) k − 1 H k + ( k = m + 1 ∑ ∞ k ( − 1 ) k − 1 ) H m Now the second term is O ( m ln m ) as m → ∞ , and hence m → ∞ lim n = 1 ∑ m n 1 ( k = 1 ∑ n − 1 k ( − 1 ) k ) − ln ( 2 ) H m = k = 1 ∑ ∞ k ( − 1 ) k − 1 H k which I proved elsewhere to be equal to 2 1 ζ ( 2 ) − 2 1 ( ln 2 ) 2 = 1 2 1 π 2 − 2 1 ( ln 2 ) 2 which makes the answer 2 + 1 2 + 2 + 2 = 1 8 .