Demo:  range

The range operator creates an observable data stream with a starting number and a count.

//Hint: On the timescale above the output will look overlapped
let input = range(10, 5);//start = 10 & count = 5

//let's add 1sec delay after each data to remove the overlap
let process = concatMap(v => of(v).pipe(delay(1000)));

let output = input.pipe(process).subscribe(v=>console.log(v))