Bonjour,
[tex]U_{n + 1} = (U_{n} + 2)(U_{n} - 1)[/tex]
[tex]U_{1} = (U_{0} + 2)(U_{0} - 1)[/tex]
[tex]U_{1} = ( - 3 + 2)( - 3 - 1) = - 1 \times ( - 4) = 4[/tex]
[tex]U_{2} = (U_{1} + 2)(U_{1} - 1)[/tex]
[tex]U_{2} = (4+ 2)(4 - 1) = 6 \times 3 = 18[/tex]
[tex]U_{3} = (U_{2} + 2)(U_{2} - 1)[/tex]
[tex]U_{3} = (18+ 2)(18- 1) = 20 \times 17 = 340[/tex]