**Given:**

a_{9} = 19

a + 8d = 19 (i)

**Acc. to question,**

a_{19 }= 3a_{6} (ii)

a_{19 }= a + 18d

a_{6 }= a + 5d

**Putting the value of a**_{19} and a_{6 }in (ii)

a + 18d = 3(a +5d)

3d = 2a

3d = 2(19 - 8d) (from (i))

19d = 38

d = 2

**Now, putting the value of d in (i)**

a = 19 - 8(2) = 3

a_{1} = a = 3

a_{2} = a +d = 3 +2 = 5

a_{3} = a +2d = 3 + 2(2) = 7

**Hence, the A.P. is 3, 5, 7, 9,.....**