\[c_{1} = 3;\ \ c_{n + 1} = c_{n} + 4\]
\[c_{2} = 3 + 4 = 7;\]
\[c_{3} = 7 + 4 = 11;\]
\[c_{4} = 11 + 4 = 15;\]
\[c_{5} = 15 + 4 = 19.\]