How to spot them
Take a positive integer k. Find its divisors. Find the distinct prime factors of each divisor. Sum all these factors together. If this number (sum) is a divisor of k (if the sum divides k) then, this number k, is a BIU number
Examples
Let's take the number 54
Find all the divisors: [1, 2, 3, 6, 9, 18, 27, 54]
Find the distinct prime factors of each divisor
NOTE: For the case of 1
we take as distinct prime factor 1
1 -> 1
2 -> 2
3 -> 3
6 -> 2,3
9 -> 3
18 -> 2,3
27 -> 3
54 -> 2,3
Now we take the sum of all these prime factors
1+2+3+2+3+3+2+3+3+2+3=27
27
divides 54 (leaves no remainder)
So, 54
is a BIU number.
Another (quick) example for k=55
Divisors: [1,5,11,55]
Sum of distinct prime factors: 1+5+11+5+11=33
33
is NOT a divisor of 55, that's why 55
is NOT a BIU number.
BIU numbers
Here are the first 20 of them:
1,21,54,290,735,1428,1485,1652,2262,2376,2580,2838,2862,3003,3875,4221,4745, 5525,6750,7050...
but this list goes on and there are many BIU numbers that are waiting to be descovered by you!
The Challenge
Given an integer n>0
as input, output the nth BIU number
Test Cases
Input->Output
1->1
2->21
42->23595
100->118300
200->415777
300->800175
This is codegolf.Shortest answer in bytes wins!
1
is not prime... \$\endgroup\$