If the result to be proved starts from n "2.3.4 ..., it will not start from N= 1, depending on the conclusion of the proof.

A proof method of natural number n related proposition in mathematics. Must include two steps:

(1) Verify that the proposition is correct when n takes the first natural value n = n 1 (n 1 = 1, 2 or other constants);

(2) Assuming that the proposition is correct when n takes the natural number k, it is also correct when n=k+ 1.

Therefore, it can be concluded that this proposition holds for all natural numbers starting from n 1

Image, the effect is like a domino effect.