Sequence of odd natural numbers is 1, 3, 5, 7, …
This sequence is an A.P. with
a = 1, d = 3 – 1 = 2
\(\therefore\) The nth term of the sequence of odd natural numbers is 2n – 1.
Sequence of even natural numbers is 2, 4, 6, 8, …
This sequence is an A.P. with a = 2, d = 4 – 2 = 2
\(\therefore\) The nth term of the sequence of even natural numbers is 2n.