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 12:55, 28 January 2022
, 2 years agoRealize in F#
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=={{header|F_Sharp|F#}}==
Can anything be described as a translation of J? I use a wheel as described in J's comments, but of course I use numerical methods not euyuk! strings.
<lang fsharp>
// Composite numbers k with no single digit factors whose factors are all substrings of k. Nigel Galloway: January 28th., 2022
let fG n g=let rec fN i g e l=match i<g,g=0L,i%10L=g%10L with (true,_,_)->false |(_,true,_)->true |(_,_,true)->fN(i/10L)(g/10L) e l |_->fN l e e (l/10L) in fN n g g (n/10L)
let fN(g:int64)=Open.Numeric.Primes.Prime.Factors g|>Seq.skip 1|>Seq.distinct|>Seq.forall(fun n->fG g n)
Seq.unfold(fun n->Some(n|>List.filter(fun(n:int64)->not(Open.Numeric.Primes.Prime.Numbers.IsPrime &n) && fN n),n|>List.map((+)210L)))([1L..2L..209L]
|>List.filter(fun n->n%3L>0L && n%5L>0L && n%7L>0L))|>Seq.concat|>Seq.skip 1|>Seq.take 20|>Seq.iter(printfn "%d")
</lang>
{{out}}
<pre>
15317
59177
83731
119911
183347
192413
1819231
2111317
2237411
3129361
5526173
11610313
13436683
13731373
13737841
13831103
15813251
17692313
19173071
28118827
Real: 00:00:26.059
</pre>
=={{header|J}}==
<lang J> */2 3 5 7
210
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