Find the nth term in the series: 3, 7, 11, 15, 19

Find the difference between each value. 7-3, 11-7 ... For this series the difference is 4. The nth term is then 4n + or - a constant. The series is 3, 7, 11.. each of these is 1 below a multiple of 4. 41- 1 =3 42- 1=7 and so on. So the nth term would be 4n-1 ....