The lazy sequence of results returned by SComb.permutations/1, SComb.combinations/2, SComb.subsets/1, SComb.selections/2, SComb.partitions/1, SComb.combinations_with_replacement/2, SComb.permuted_combinations/2 and SComb.cartesian_product/1.

A sequence is an Enumerable that generates its elements one at a time, like a Stream. In addition it knows its size and how to find an element by its index, so functions such as Enum.count/1, Enum.at/2, Enum.slice/2, Enum.take/2 with a negative amount and Enum.random/1 do not generate the elements before the ones asked for:

iex> sequence = SComb.permutations(1..30)
iex> Enum.count(sequence)
265252859812191058636308480000000
iex> Enum.at(sequence, 10 ** 30) |> Enum.take(3)
[14, 28, 9]

Indexing is only used for inputs of moderate size, as the size of the sequence has to be cheap to find. For larger inputs the sequence is streamed, and Enum.count/1 still returns the size.