Progression03: Sum of Odd and Even Numbers

Sum of first n odd numbers

S = $n^2$

Number of terms(n), if nth term of odd-number series is $t_n$ 

n =  $\dfrac{t_n+1}{2}$

Sum of first n even numbers

S = n(n+1)

Number of terms(n), if nth term of even-number series is $t_n$ 

n =  $\dfrac{t_n}{2}$