The nth triangular number is given by n * (n + 1) / 2. Create a sequence of the first 20 triangular numbers. R has a built-in constant, letters, that contains the lowercase letters of the Roman...

The nth triangular number is given by n * (n + 1) / 2. Create a sequence of the

first 20 triangular numbers. R has a built-in constant, letters, that contains the

lowercase letters of the Roman alphabet. Name the elements of the vector that you

just created with the first 20 letters of the alphabet. Select the triangular numbers

where the name is a vowel. [10]