src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Flowable<Integer> range(int start, int count) {
        if (count < 0) {
            throw new IllegalArgumentException("count >= 0 required but it was " + count);
        } else
        if (count == 0) {
            return empty();
        } else
        if (count == 1) {
            return just(start);
        } else
        if ((long)start + (count - 1) > Integer.MAX_VALUE) {
            throw new IllegalArgumentException("Integer overflow");
        }
        return RxJavaPlugins.onAssembly(new FlowableRange(start, count));
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Flowable<Integer> range(int start, int count) {
        if (count < 0) {
            throw new IllegalArgumentException("count >= 0 required but it was " + count);
        } else
        if (count == 0) {
            return empty();
        } else
        if (count == 1) {
            return just(start);
        } else
        if ((long)start + (count - 1) > Integer.MAX_VALUE) {
            throw new IllegalArgumentException("Integer overflow");
        }
        return RxJavaPlugins.onAssembly(new FlowableRange(start, count));
    }
Returns a Flowable that emits a sequence of Integers within a specified range.
<p>
<img width="640" height="195" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/range.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream and signals values on-demand (i.e., when requested).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code range} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param start
the value of the first Integer in the sequence
@param count
the number of sequential Integers to generate
@return a Flowable that emits a range of sequential Integers
@throws IllegalArgumentException
if {@code count} is less than zero, or if {@code start} + {@code count} &minus; 1 exceeds
{@code Integer.MAX_VALUE}
@see <a href="http://reactivex.io/documentation/operators/range.html">ReactiveX operators documentation: Range</a>