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A261034
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Numbers m such that 3*m is squarefree.
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9
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1, 2, 5, 7, 10, 11, 13, 14, 17, 19, 22, 23, 26, 29, 31, 34, 35, 37, 38, 41, 43, 46, 47, 53, 55, 58, 59, 61, 62, 65, 67, 70, 71, 73, 74, 77, 79, 82, 83, 85, 86, 89, 91, 94, 95, 97, 101, 103, 106, 107, 109, 110, 113, 115, 118, 119, 122, 127, 130, 131
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OFFSET
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1,2
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COMMENTS
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Squarefree numbers divisible by 3: 3, 6, 15, 21, 30, 33, 39, 42, 51, 57, 66, 69, 78, 87, 93, 102, ...
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n)^s = (3^s)*zeta(s)/((1+3^s)*zeta(2*s)), s>1. - Amiram Eldar, Sep 26 2023
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EXAMPLE
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10 is in this sequence because 3*10 = 30 is squarefree.
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MAPLE
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select(numtheory:-issqrfree, [seq(seq(3*i+j, j=1..2), i=0..1000)]); # Robert Israel, Aug 07 2015
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MATHEMATICA
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PROG
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(Magma) [n: n in [1..200] | IsSquarefree(3*n)];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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