# Member of a list

This list is given by $$a_1 = 2, a_2 = 3, a_n = 2 \dfrac{a_{n-1}}{a_{n-2}} + 3a_{n-1}, \text{ for } n>2$$

Find the 30th element of the list. Print the first 20 elements in a table and sort them in descending order.

Please help me how to begin. I have not been working with this program for a long time. Tell me how to input the given and get the elements in a table in descending order.

You can define recursive functions almost exactly the way you have written it in your question:

a[n_] := a[n] = 2 a[n - 1]/a[n - 2] + 3 a[n - 1];
a[1] = 2;
a[2] = 3;


Now you can find the 30th element by typing

 a[30]


and you can find a range of values:

a[#]&/@Range[20]


Use Sort to sort them.

• Thank you for helping but it does not come correct.I might write it inncorect,so I edited it now.They are subscripts of a. – User Sep 4 at 19:58