1.

Formula method, when the meaning of the first n terms and sn of a sequence is known in the question, an=sn-s(n- 1) can be obtained according to the formula.

2.

Undetermined coefficient method: If the topic features conform to the recurrence relation A 1 = A, AN+ 1 = Ban+C (A, B, C are constants, B≠ 1, C≠0), geometric series can be constructed by undetermined coefficient method, and its general term formula can be found.

3.

Item-by-item addition: If the topic characteristics conform to the recurrence relation A 1 = A (A is constant) and an+ 1=an+f(n), the general term formula of the series can be obtained by adding the difference.

4.

Item-by-item connection method: If the topic characteristics conform to the recurrence relation a 1=A(A is constant), an+ 1=f(n)? The general term formula of the series can be obtained by ratio multiplication.

5.

Reciprocal method: If the topic characteristics conform to the recurrence relation A 1 = A, BAN+CAN+1+DAAN+1= 0, (A, B, C and D are constants), the general term formula of the series can be obtained by reciprocal method.

6.

Other methods of observation or induction, etc.