Catalan numbers are a sequence of natural numbers that occurs in many interesting counting problems like following.
1) Count the number of expressions containing n pairs of parentheses which are correctly matched. For n = 3, possible expressions are ((())), ()(()), ()()(), (())(), (()()).

2) Count the number of possible Binary Search Trees with n keys (See this)

When you mouse over and click to add a search term this(these) boolean operator(s) is(are) not implied. (select all that apply)?

Drag the tiles to the correct boxes to complete the pairs. match the errors with their definitions. #name #value #ref when a formula produces output that is too lengthy to fit in the spreadsheet cell arrowright when you enter an invalid cell reference in a formula arrowright when you type text in cells that accept numeric data arrowright when you type in a cell reference that doesn’t exist arrowright reset next

Brian wants to conduct an online search with a certain phrase. he intends to use the words books that belong to the 1800s in his search. how should he use the word that in his search?