Factorial in SQL

Example for versions PostgreSQL 9.1

The task of factorials calculation is solved using standard methods only: a built-in factorial function ! (postfix form; there is also a prefix form !!) and a set function generate_series which generates a set of rows containing values between the first and the second parameters. 

select n || '! = ' || (n!)
  from generate_series(0,16) as seq(n);