5- -5 please someone I can use the help thank you!

Consider the sequence below. 3 , 1 , 1/3 , 1/9 , select the explicit function which defines the sequence.

Who can me with this algebra for your guys.

Q1 how many whole numbers less than 1000 can be written as a product of 3 consecutive whole numbers? a)10 b)11 c)15 d)21 q2 how many whole numbers between 5000 and 6000 consist of four different digits that decrease from left to right? a)3 b)10 c)69 d)120