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 A123623 Smallest k>1 such that mu(n*k) = mu(n), where mu=A008683. 3
 6, 15, 10, 2, 6, 35, 6, 2, 2, 21, 6, 2, 6, 15, 14, 2, 6, 2, 6, 2, 10, 15, 6, 2, 2, 15, 2, 2, 6, 77, 6, 2, 10, 15, 6, 2, 6, 15, 10, 2, 6, 55, 6, 2, 2, 15, 6, 2, 2, 2, 10, 2, 6, 2, 6, 2, 10, 15, 6, 2, 6, 15, 2, 2, 6, 35, 6, 2, 10, 33, 6, 2, 6, 15, 2, 2, 6, 35, 6, 2, 2, 15, 6, 2, 6, 15, 10, 2, 6, 2, 6, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) = A123624(n) / n. From Robert Israel, Apr 02 2017: If n is squarefree, a(n) is the product of the least two primes coprime to n. Otherwise a(n) = 2. (End) LINKS R. Zumkeller, Table of n, a(n) for n = 1..10000 MAPLE a:= proc(n) local r, p, count;   if not numtheory:-issqrfree(n) then return 2 fi;   r:= 1; count:= 0; p:= 1;   do     p:= nextprime(p);     if n mod p > 0 then       count:= count+1;       r:= r*p;       if count = 2 then return r fi     fi   od end proc: map(a, [\$1..1000]); # Robert Israel, Apr 02 2017 MATHEMATICA a[n_] := Module[{r = 1, p = 1, count = 0}, If[!SquareFreeQ[n], Return[2]]; While[True, p = NextPrime[p]; If[Mod[n, p] > 0, count++; r = r*p; If[count == 2, Return[r]]]]]; Array[a, 100] (* Jean-François Alcover, Feb 13 2018, after Robert Israel *) CROSSREFS Cf. A093316. Sequence in context: A289722 A070870 A202749 * A240990 A215739 A161397 Adjacent sequences:  A123620 A123621 A123622 * A123624 A123625 A123626 KEYWORD nonn AUTHOR Reinhard Zumkeller, Oct 03 2006 EXTENSIONS Name corrected by Robert Israel, Apr 02 2017 STATUS approved

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Last modified September 28 01:27 EDT 2021. Contains 347698 sequences. (Running on oeis4.)