the series is not absolutely convergent ... use the integral test.
The series is :
The absolut series is :
But I'm stuck at this very (easy ?) step :
But I can't determine, in my head, if it is convergent or not. I feel really dumb.
If I compare to the harmonic series, each term is lower.
The "quotient test" gives me :
What is the tiny thing I missed ?
Thanks for your help !