Mathematics - Sequence & Series Question with Solution | TestHub

Let $S_n=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\dots$ upto $n$ terms. If the sum of the first six terms of an A.P. with first term -p and common difference p is $\sqrt{2026{\mathrm{S}}_{2025}}$, then the absolute difference betwen $20^{\text{th }}$ and $15^{\text{th }}$ terms of the A.P. is