Ultra useful primes: Difference between revisions

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 <pre>1 3 5 15 5 59 159 189 569 105
 2549 2439</pre>
+=={{header|Ring}}==
+see "works..." + nl
+limit = 10
+for n = 1 to limit
+    k = 0
+    flag = 0
+    while true
+          k++
+          num = pow(2,pow(2,n)) - k
+          if isPrime(num)
+             flag = 1
+             exit
+          ok
+    end
+    if flag = 1
+       see "n = " + n + " k = " + k + nl
+    ok
+next
+see "done.." + nl
+func isPrime num
+     if (num <= 1) return 0 ok
+     if (num % 2 = 0 and num != 2) return 0 ok
+     for i = 3 to floor(num / 2) -1 step 2
+         if (num % i = 0) return 0 ok
+     next
+     return 1
+<syntaxhighlight lang="ring">
+{{out}}
+<pre>
+works...
+n = 1 k = 1
+n = 2 k = 3
+n = 3 k = 5
+n = 4 k = 15
+n = 5 k = 5
+n = 6 k = 59
+n = 7 k = 159
+n = 8 k = 189
+n = 9 k = 569
+n = 10 k = 105
+done...
+</pre>
 =={{header|Ruby}}==