Composite numbers k with no single digit factors whose factors are all substrings of k: Difference between revisions
Composite numbers k with no single digit factors whose factors are all substrings of k (view source)
Revision as of 06:49, 14 July 2023
, 10 months agorust example
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3129361
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=={{header|Rust}}==
<syntaxhighlight lang="rust">use primes::{is_prime,factors_uniq};
/// True if non-prime n's factors, all > 9, are all substrings of its representation in base 10
fn contains_its_prime_factors_all_over_7(n: u64) -> bool {
if n < 10 || is_prime(n) {
return false;
}
let strn = &n.to_string();
let pfacs = factors_uniq(n);
return pfacs.iter().all(|f| f > &9 && strn.contains(&f.to_string()));
}
fn main() {
let mut found = 0;
// 20 of these < 30 million
for n in 0..30_000_000 {
if contains_its_prime_factors_all_over_7(n) {
found += 1;
print!("{:12}{}", n, {if found % 10 == 0 {"\n"} else {""}});
if found == 20 {
break;
}
}
}
}
</syntaxhighlight>{{out}}
<pre>
15317 59177 83731 119911 183347 192413 1819231 2111317 2237411 3129361
5526173 11610313 13436683 13731373 13737841 13831103 15813251 17692313 19173071 28118827
</pre>
=={{header|Sidef}}==
<syntaxhighlight lang="ruby">var e = Enumerator({|f|
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