I have a sequence (with unique elements): $a = (1,4,9)$. Is there a short notation for the same set, but without the last element: $b = (1,4)$?
I came up with one solution, which simple removes the last item by index: $$b =a \setminus \{ a_{|a|-1}\}$$ or by taking all except the last: $$b = (a_0,...,a_{|a|-2})$$
However i am hoping to find something shorter, like $a_{-1}$ or something in that direction. Is there a standard way of doing this?
Sometimes notation like $$(a_1,\ldots,\widehat{a_k},\ldots,a_n)=(a_1,\ldots,a_{k-1},a_{k +1},\ldots,a_n)$$ is used. The element with the hat is omitted. There are ways to shorten it further, such as $$(a_{\widehat{k}})$$