Such as: 1, 4, 9, 16, ...

Comparison 1, 2, 3, 4, ....

Obviously a (n) = n 2.

2. Compare the sum of the figures before and after.

Such as: 1, 1, 2, 3, 5, 8, .......

Obviously, the sum of the first two is equal to the third, a(n)=a(n-2)+a(n- 1), (n & gt=3). (Fibonacci series)

Another example is: 1, 2,4,7, 1 1, 16. .....

Is the former term plus the natural sequence equals the latter term. a(n)=a(n- 1)+(n- 1)，(n & gt=2).

Another example is:

3,4,6,9, 13 ....

3,4,6,9, 14 ....

Look at these two series, and then how to write?

The first one is: adding natural sequence; The second is the addition of the first two items-1. So write it down as follows:

3,4,6,9, 13, 18,24 ....

3,4,6,9, 14,22,35 ....

3. Look at the relationship between things.

Such as 1, 1, 3, 4, 5, 9, 7, 16. ....

If viewed separately, it is: 1, 3, 5, 7 and 1, 4, 9, 16.

Singular numbers are odd columns, and even numbers are the squares of natural numbers.

A lot, just say these simple things, I hope I can help you.