Analysis:

The first number is followed by "1", the second number is based on 0+5 = 5, 5+ 10 = 15, followed by 15+ 15=30.

Find the meaning of the fill-in-the-blank rule.

In fact, it is to strengthen the familiarity with the general law of sequence. Although it has many solutions, it mainly cultivates your ability to discover the general law of series and guess the general term of series (that is, the ability to use incomplete induction);

So that when we encounter some series whose general terms are difficult to find by general methods, we can quickly and accurately guess the general term formula of this series through the first few terms, and then prove it by mathematical induction or reduction to absurdity or other methods, bypassing the main mountain and quickly getting its general term formula. Therefore, finding the rules to fill in the blanks will still help us to enhance our understanding of some difficulties and characteristic series.