Frobenius numbers

Frobenius numbers is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Task

a(n) = prime(n)*prime(n+1) - prime(n) - prime(n+1), where prime(n) < 10,000

REXX

<lang rexx></lang>

Ring

<lang ring> load "stdlib.ring"

decimals(0) see "working..." + nl see "Frobenius numbers are:" + nl

row = 0 limit1 = 101 Frob = []

for n = 1 to limit1

   if isprime(n)
      add(Frob,n)
   ok

next

for n = 1 to len(Frob)-1

   row = row + 1
   fr = Frob[n]*Frob[n+1]-Frob[n]-Frob[n+1]
   see "" + fr + " "
   if row%5 = 0
      see nl
   ok

next

see "Found " + row + " Frobenius primes" + nl see "done..." + nl </lang>

Output:

working...
Frobenius primes are:
1 7 23 59 119 
191 287 395 615 839 
1079 1439 1679 1931 2391 
3015 3479 3959 4619 5039 
5615 6395 7215 8447 9599 
Found 25 Frobenius primes
done...