How ad an increasing index to a query result?

Hello,

Could somebody please try to help me with this problem?
So, let’s say that I have the query:

CREATE SEQUENCE c START 1;

SELECT a, nextval('c') as b
FROM table1
ORDER BY a DESC LIMIT 5;

I.e., I want to pick the 5 largest entries from table1 and show them
alongside a new index column that tells the position of the entry. For
example:

 a  | b
--------
82 | 5
79 | 4
34 | 3
12 | 2
11 | 1

However, when I try this approach, the values of column b don’t follow
the correct order. How should I go about and modify my code?