C#

// Pre-append the value to the front of the instance, so in this case it would render 3, 2, 1
    var observable = Observable.Empty<int>()
    .StartWith(1)
    .StartWith(2)
    .StartWith(3);
observable.Subscribe(Console.WriteLine);

var enumerable = Enumerable.Range(1, 10);
var observable = enumerable.ToObservable();
observable.Subscribe(Console.WriteLine);

// Generate a sequence IObservable from 1 to 10
var observable = Observable.Generate(
    1,                        // Initial value
    value => value <= 10,    // Predicate
    value => value,            // Selector
    value => value + 1);    // Iterator
observable.Subscribe(Console.WriteLine);