If the value of above expression is in the form , where and are positive integers with , find .
Bonus : Generalise it.
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L e t C = i = a ∑ b n = p ∏ q ( i + n ) 1 = q − p 1 ⋅ i = a ∑ b ( n = p ∏ q − 1 ( n + i ) 1 − n = p + 1 ∏ q ( n + i ) 1 )
(A TELESCOPIC SERIES)
= q − p 1 ( n = p ∏ q − 1 ( a + n ) 1 − n = p + 1 ∏ q ( b + n ) 1 )
C = q − p 1 ( ( a + q − 1 ) ! ( a + p − 1 ) ! − ( b + q ) ! ( b + p ) ! )
For this question a = p = 1 , q = 2 0 1 7 and b → ∞ ∴ i = 1 ∑ ∞ ∏ n = 1 2 0 1 7 ( i + n ) 1 = 2 0 1 6 × 2 0 1 7 ! 1 ∴ 2 0 1 6 + 2 0 1 7 = 4 0 3 3
Assumptions: ( p = q , ( n + i ) = 0 , a < b , p < q ) ∀ i , n , a , b , p , q ∈ Z +