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A007424
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a(n) = 1 if n is squarefree, otherwise 2.
(Formerly M0060)
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2
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1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 2, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 2
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OFFSET
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1,4
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Antti Karttunen, Table of n, a(n) for n = 1..65537
Index entries for sequences computed from exponents in factorization of n
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FORMULA
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a(n) = 2 - A008966(n). - Antti Karttunen, Nov 18 2017
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MATHEMATICA
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f[n_]:=Union[Last/@FactorInteger[n]][[ -1]]; lst={1}; Do[If[f[n]==1, AppendTo[lst, 1], AppendTo[lst, 2]], {n, 2, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Mar 07 2010 *)
Table[If[SquareFreeQ[n], 1, 2], {n, 100}] (* Harvey P. Dale, Jul 09 2014 *)
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PROG
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(MuPAD) func(2-abs(numlib::moebius(n)), n):
(PARI) A007424(n) = (2-issquarefree(n)); \\ Antti Karttunen, Nov 18 2017
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CROSSREFS
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Cf. A005117, A008966, A107078.
Sequence in context: A037306 A194799 A291119 * A323308 A278908 A307848
Adjacent sequences: A007421 A007422 A007423 * A007425 A007426 A007427
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KEYWORD
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easy,nonn
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AUTHOR
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N. J. A. Sloane
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STATUS
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approved
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