Mathematics - Straight line Question with Solution | TestHub

$\begin{array}{rl}& 1^{\text{st }}\text{ term }\to 1,2^{\text{nd }}\text{ term }=2,4^{\text{th }}\text{ term }\to 3,\\ & 7^{\text{th }}\text{ term }\to 4,11^{\text{th }}\text{ term }\to 5,\dots \end{array}$ Series is $1,2,4,7,11,\dots$ $a_n=1+\frac{n(n-1)}{2}=\frac{n^2-n+2}{2}$ If $n=14$, then $a_n=92,\mathrm{If}n=15$, then $a_n=106$.