Kata

Every positive integer number, that is not prime, may be decomposed in prime factors. For example the prime factors of 20, are:

2, 2, and 5, because: 20 = 2 . 2 . 5

The first prime factor (the smallest one) of 20 is 2 and the last one (the largest one) is 5. The sum of the first and the last prime factors, sflpf of 20 is: sflpf = 2 + 5 = 7

The number 998 is the only integer in the range [4, 1000] that has a value of 501 , so its sflpf equals to 501, but in the range [4, 5000] we will have more integers with sflpf = 501 and are: 998, 1996, 2994, 3992, 4990.

We need a function sflpf_data() (javascript: sflpfData()that receives two arguments, val as the value of sflpf and nMax as a limit, and the function will output a sorted list of the numbers between 4 to nMax(included) that have the same value of sflpf equals to val.

Let's see some cases:

sflpf_data(10, 100) == [21, 25, 63]
/// the prime factorization of these numbers are:
Number  Prime Factorization     Sum First and Last Prime Factor
21       = 3 . 7      ---->                 3 + 7 = 10
25       = 5 . 5      ---->                 5 + 5 = 10
63       = 3 . 3 . 7  ---->                 3 + 7 = 10

sflpf_data(10, 200) == [21, 25, 63, 105, 125, 147, 189]
sflpf_data(15, 150) == [26, 52, 78, 104, 130]

(Advice:Try to discard primes in a fast way to have a more agile code)

Enjoy it!