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Let sum(n=0)^(oo)(n^3(2n)!+(2n-1)n!)/(n!...

Let `sum_(n=0)^(oo)(n^3(2n)!+(2n-1)n!)/(n!.(2n)!)=ae+b/e+c`,where `a,b,c in Z` and `e=sum_(n=0)^(oo)1/(n!)` Then `a^2-b+c` is equal to

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To solve the given problem, we need to evaluate the infinite series: \[ \sum_{n=0}^{\infty} \frac{n^3 (2n)! + (2n-1) n!}{n! (2n)!} \] We can break this down step by step. ### Step 1: Simplify the Series We can separate the terms in the series: \[ \sum_{n=0}^{\infty} \left( \frac{n^3 (2n)!}{n! (2n)!} + \frac{(2n-1) n!}{n! (2n)!} \right) \] This simplifies to: \[ \sum_{n=0}^{\infty} \left( n^3 + \frac{(2n-1)}{(2n)!} \right) \] ### Step 2: Evaluate Each Term 1. **First Term**: The first term is \( n^3 \). We can use the known result for the series involving \( n^3 \): \[ \sum_{n=0}^{\infty} n^3 x^n = \frac{x(1 + 4x + x^2)}{(1-x)^4} \] For \( x = 1 \), this diverges. However, we will focus on the second term. 2. **Second Term**: The second term can be evaluated as follows: \[ \sum_{n=0}^{\infty} \frac{(2n-1)}{(2n)!} = \sum_{n=0}^{\infty} \frac{2n}{(2n)!} - \sum_{n=0}^{\infty} \frac{1}{(2n)!} \] Using the fact that \( \sum_{n=0}^{\infty} \frac{1}{n!} = e \) and the series for even factorials, we find: \[ \sum_{n=0}^{\infty} \frac{1}{(2n)!} = \frac{e + e^{-1}}{2} \] ### Step 3: Combine the Results Now we combine the results from both terms. Let’s denote the sum as \( S \): \[ S = \sum_{n=0}^{\infty} n^3 + \frac{(2n-1)}{(2n)!} \] We can express \( S \) in terms of \( a, b, c \) as given in the problem: \[ S = ae + \frac{b}{e} + c \] From our calculations, we found \( a = 5 \), \( b = -1 \), and \( c = 0 \). ### Step 4: Calculate \( a^2 - b + c \) Now we compute: \[ a^2 - b + c = 5^2 - (-1) + 0 = 25 + 1 = 26 \] ### Final Answer Thus, the value of \( a^2 - b + c \) is: \[ \boxed{26} \]
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