(r + 1)(2r + 5)
n = 5.
Yes for example 5+11 = 16
that would be 215, so no. it is divisible by 5, so that means it is not prime.
But 5+5 = 10 and 5 is a prime number
2 + 3 = 5 Two plus any odd prime number is odd.
A prime plus another prime is at the very least going to be an even number since all primes (with the exception of 2) are odd.
Thirty
Note that the reason there exists a technique called multiplication is so that we do not have to perform tedious and lengthy series of addition such as the one you have presented. So, you have given us 24 of the number 5 to add. 24 x 5 = 120. (Addition form) 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 120
2 x 3 x 5 + 1 = 31
5 is prime
5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 55