Ответ: \[a_{n} = 3 - 2n\] \[a_{1} = 3 - 2 = 1\] \[a_{2} = 3 - 4 = - 1\] \[a_{3} = 3 - 6 = - 3\] \[a_{4} = 3 - 8 = - 5\]