20 and 30 are rectangular numbers (4 * 5 and 5 * 6). There are none in between them.
If those are feet, and you are talking about a rectangular box, then just multiply the numbers. If the numbers are any other unit (and you are still talking about a rectangular box), then convert each of the numbers to feet first.
Rectangular numbers are a subset of composite numbers. The squares of prime numbers will be composite but not rectangular.
The first 20 odd numbers are: 13579111315171921232527293133353739.
The first 20 digets after the dot in pi are: 3.14159265358979323846
Rectangular numbers are of the form n(n+1) for n = 1, 2, 3, 4, 5, 6, ... The first few rectangular numbers are: 2, 6, 12, 20, 30, 42, ...
20 and 30 are rectangular numbers (4 * 5 and 5 * 6). There are none in between them.
If those are feet, and you are talking about a rectangular box, then just multiply the numbers. If the numbers are any other unit (and you are still talking about a rectangular box), then convert each of the numbers to feet first.
Rectangular numbers are a subset of composite numbers. The squares of prime numbers will be composite but not rectangular.
The first 20 odd numbers are: 13579111315171921232527293133353739.
The prime numbers and the squares of primes between 2 and 20: 3, 4, 5, 7, 9, 11, 13, 17 and 19.
1 2 3 4 5
The second and third rectangular numbers are 6 and 12
the first 20, arre... 3.1459265358979323846
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.
So far I know that 120 is a rectangular number
rectangular numbers are numbers just displayed in the shape of a rectangle e.g take the number 6 it can be shown as: ** ** or ****** **