Let ∑123456789n=03n2+9n+7(n2+3n+2)3=ab, where a and b are relatively prime positive integers. Find b−a.
This is what Wolfram/Alpha gives as the sum which appears to be an irrational number !!!
https://www.wolframalpha.com/input/?i=%E2%88%91%5B+%283n%5E2+%2B+9n+%2B+7%29+%2F+%28n%5E2+%2B+3n+%2B2%29%5E2%2C+n%2C+0%2C+123456789+%5D
∑[ (3n^2 + 9n + 7) / (n^2 + 3n +2)^2, n, 0, 123456789 ] =3.289868109.............etc.