The following two sets were generated by the same process.
The first set is easy to handle the second is more complicated. Hope no hints will be needed:

Easy: {1,2,3,4,5,6,8,9,10,11,12,13,14}.
Diff: {2,7,9,10,12,17,19,21,23,28,30,31,33,38,40}

Good luck