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A269870
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Numbers coprime to the number of their odd divisors.
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2
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1, 2, 3, 4, 5, 7, 8, 11, 13, 15, 16, 17, 19, 21, 23, 25, 27, 29, 31, 32, 33, 35, 37, 39, 41, 43, 47, 49, 50, 51, 53, 55, 57, 59, 61, 64, 65, 67, 69, 71, 73, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 98, 100, 101, 103, 105, 107, 109, 111, 113, 115, 119, 121, 123, 125, 127, 128, 129, 131, 133, 135, 137, 139, 141, 143, 145, 149, 151, 155
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OFFSET
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1,2
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COMMENTS
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Conjecture: the asymptotic density of this sequence is the same as that of A046642.
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LINKS
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EXAMPLE
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For n=2, a(2)=2 is a term as the number of odd divisors of 2 is 1, which is coprime to 2.
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MATHEMATICA
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Select[Range@200, CoprimeQ[#, Length@Select[Divisors[#], OddQ]]&]
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PROG
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(PARI) for(n=1, 200, gcd(n, sumdivmult(n, d, d%2))==1&&print1(n, ", "))
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CROSSREFS
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Cf. A001227 (number of odd divisors), A046642 (numbers coprime to the number of their divisors), A269818 (counterpart for the number of even divisors).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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