Let the general formula of this series be An=|3n- 1|, that is, the absolute value of (3n- 1), where n is an integer greater than or equal to 0.

Then it is |3*0- 1|= 1, | 3 * 1+0 | = 2, |3*2- 1|=5, | 3 * 3- 1 |.

That is, the fifth number is 1 1. The sixth number is 14, and so on.

Does it meet the requirements? There may be other answers!