Combinations with repetitions/Square digit chain: Difference between revisions

To achieve reasonable performance, the Kotlin entry for the [[Iterated digits squaring]] task used a similar approach to that required by this task for k = 8.

So the following generalizes that code to deal with values of k up to 17 (which requires 64 bit integers) and to identify numbers where the squared digits sum sequence eventually ends in 1 rather than 89, albeit the sum of both must of course be 10 ^ k - 1.