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A227291
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Characteristic function of squarefree numbers squared (A062503).
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9
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1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0
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OFFSET
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1,1
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LINKS
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FORMULA
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Dirichlet g.f.: zeta(2s)/zeta(4s) = prod[prime p: 1+p^(-2s) ], see A008966.
Multiplicative with a(p^e) = 1 if e=2, a(p^e) = 0 if e=1 or e>2. - Antti Karttunen, Jul 28 2017
(End)
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EXAMPLE
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a(3) = 0 because 3 is not the square of a squarefree number.
a(4) = 1 because sqrt(4) = 2, a squarefree number.
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MAPLE
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local pe;
if n = 0 then
1;
else
for pe in ifactors(n)[2] do
if op(2, pe) <> 2 then
return 0 ;
end if;
end do:
end if;
1 ;
end proc:
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MATHEMATICA
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Table[Abs[Sum[MoebiusMu[n/d], {d, Select[Divisors[n], SquareFreeQ[#] &]}]], {n, 1, 200}] (* Geoffrey Critzer, Mar 18 2015 *)
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PROG
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(PARI) a(n)=if(n<1, 0, direuler(p=2, n, 1+X^2)[n])
(Haskell)
a227291 n = fromEnum $ (sum $ zipWith (*) mds (reverse mds)) == 1
where mds = a225817_row n
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CROSSREFS
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Cf. A000196, A007427, A008836, A008683, A008966, A010052, A027750, A037213, A225546, A225569, A225817, A307430, A322327, A355448.
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KEYWORD
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nonn,mult,easy
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AUTHOR
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STATUS
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approved
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