20 lines
703 B
Plaintext
20 lines
703 B
Plaintext
fcn mobius(n){
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pf:=primeFactors(n);
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sq:=pf.filter1('wrap(f){ (n % (f*f))==0 }); // False if square free
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if(sq==False){ if(pf.len().isEven) 1 else -1 }
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else 0
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}
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fcn primeFactors(n){ // Return a list of prime factors of n
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acc:=fcn(n,k,acc,maxD){ // k is 2,3,5,7,9,... not optimum
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if(n==1 or k>maxD) acc.close();
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else{
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q,r:=n.divr(k); // divr-->(quotient,remainder)
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if(r==0) return(self.fcn(q,k,acc.write(k),q.toFloat().sqrt()));
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return(self.fcn(n,k+1+k.isOdd,acc,maxD)) # both are tail recursion
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}
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}(n,2,Sink(List),n.toFloat().sqrt());
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m:=acc.reduce('*,1); // mulitply factors
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if(n!=m) acc.append(n/m); // opps, missed last factor
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else acc;
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}
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