Mathematics - Sequence & Series Question with Solution | TestHub

Let$X$be the set consisting of the first$2018$terms of the arithmetic progression$\mathrm{1,6},11,\dots ,$and$Y$be the set consisting of the first$2018$terms of the arithmetic progression$\mathrm{9,16,23},\dots$. Then, the number of elements in the set$X\cup Y$is___.