Ultra useful primes: Difference between revisions

=={{header|Arturo}}==

<lang rebol>ultraUseful: function [n][

k: 1

p: (2^2^n) - k

while ø [

if prime? p -> return k

p: p-2

k: k+2

]

]

print [pad "n" 3 "|" pad.right "k" 4]

print repeat "-" 10

loop 1..10 'x [

print [(pad to :string x 3) "|" (pad.right to :string ultraUseful x 4)]

]</lang>

{{out}}

<pre> n | k

----------

1 | 1

2 | 3

3 | 5

4 | 15

5 | 5

6 | 59

7 | 159

8 | 189

9 | 569

10 | 105</pre>