Yeah I got 1.736x10^-17, 3.472x10^-17, 5.20810^-17hz the first time I did it. You let k=1,2,3 etc. right?
For comparison, two of my other approaches yielded..
5.527x10^-18Hz, 1.105x10^-17Hz and 1.658x10^-17Hz
5.52734x10^-18Hz, 5.52972x10^-18Hz and 5.53211x10^-18Hz