The problem Array Of N Elements requires to write the function that returns N items. The string serialisation of the data structure should be very specific and similar to [ 1, 2, 3 ].
In the previous solutions I've generated the items using sequences. If sequences was allowed, the solution would be trivial: let f n = seq { 1..n }. But the sequences are printed as seq [1; 2; 3] so it is need to be converted to list either with Seq.toList or List.ofSeq.
The solution is:
let f n = seq { 1..n } |> List.ofSeq