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A258211
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Nonsquarefree numbers of the form 4*k + 2.
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3
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18, 50, 54, 90, 98, 126, 150, 162, 198, 234, 242, 250, 270, 294, 306, 338, 342, 350, 378, 414, 450, 486, 490, 522, 550, 558, 578, 594, 630, 650, 666, 686, 702, 722, 726, 738, 750, 774, 810, 846, 850, 882, 918, 950, 954, 990, 1014, 1026, 1050, 1058, 1062, 1078, 1098, 1134, 1150
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OFFSET
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1,1
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COMMENTS
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The asymptotic density of this sequence is 1/4 - 2/Pi^2 = 0.047357... (A190357) - Amiram Eldar, Feb 10 2021
Even numbers whose square part is odd (and nontrivial).
If m is in the sequence then every odd multiple of m is in the sequence.
Closed under the operation A059896(.,.).
(End)
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LINKS
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FORMULA
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EXAMPLE
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18 is in this sequence because 4 * 4 + 2 = 18 = 2 * 3^2.
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MAPLE
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remove(numtheory:-issqrfree, [4*i+2 $ i=0..1000]); # Robert Israel, May 27 2015
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MATHEMATICA
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Select [Range[300], ! SquareFreeQ[(4 # - 2)] &] 4 - 2 (* Vincenzo Librandi, May 24 2015 *)
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PROG
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(Magma) [n*4+2: n in [1..300] | not IsSquarefree(4*n+2)];
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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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STATUS
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approved
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