Smallest number k such that k+2^m is composite for all m less than k: Difference between revisions
Smallest number k such that k+2^m is composite for all m less than k (view source)
Revision as of 11:25, 12 January 2022
, 2 years agoAdded Wren
Thundergnat (talk | contribs) (New draft task and Raku example) |
(Added Wren) |
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<pre>773 2131 2491 4471 5101</pre>
=={{header|Wren}}==
{{libheader|Wren-gmp}}
An embedded version as, judging by the size of numbers involved, Wren-CLI (using BigInt) will be too slow for this.
Brute force approach - takes a smidge over 2 seconds.
<lang ecmascript>import "./gmp" for Mpz
// returns true if k is a sequence member, false otherwise
var a = Fn.new { |k|
if (k == 1) return false
for (m in 1...k) {
var n = (Mpz.one << m) + k
if (n.probPrime(15) > 0) return false
}
return true
}
var count = 0
var k = 1
while (count < 5) {
if (a.call(k)) {
System.write("%(k) ")
count = count + 1
}
k = k + 2
}
System.print()</lang>
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<pre>
773 2131 2491 4471 5101
</pre>
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