matrix
It is a matrix or a determinant.
An array is a set of numbers that form some sort of regular arrangement. A linear array is a 1-dimensional array consisting of a row or a column of a set of numbers. A 2-dimensional array is a rectangular arrangement of numbers. And there are arrays with higher dimensions. The elements of an array need not be numbers: they could be variables, functions or expressions. In other words, it's a picture to describe a multiplication problem.
6
4, 6, 8, 9, 19
rectangular numbers are numbers just displayed in the shape of a rectangle e.g take the number 6 it can be shown as: ** ** or ****** **
It is a matrix or a determinant.
Rectangular numbers are a subset of composite numbers. The squares of prime numbers will be composite but not rectangular.
An array is a set of numbers that form some sort of regular arrangement. A linear array is a 1-dimensional array consisting of a row or a column of a set of numbers. A 2-dimensional array is a rectangular arrangement of numbers. And there are arrays with higher dimensions. The elements of an array need not be numbers: they could be variables, functions or expressions. In other words, it's a picture to describe a multiplication problem.
6
20 and 30 are rectangular numbers (4 * 5 and 5 * 6). There are none in between them.
'cuz
12
101
4, 6, 8, 9, 19
The second and third rectangular numbers are 6 and 12
13...13x1.
There is no such formula. Rectangular numbers are composite numbers and there is no known formula that will generate either composite numbers or prime numbers.