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A347877
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Numbers k for which A003415(sigma(k)) is odd.
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6
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2, 4, 5, 9, 10, 13, 16, 17, 20, 25, 26, 29, 32, 34, 37, 40, 41, 45, 52, 53, 58, 61, 64, 68, 72, 73, 74, 80, 82, 89, 90, 97, 98, 101, 104, 106, 109, 113, 116, 117, 122, 128, 136, 137, 146, 148, 149, 153, 157, 160, 162, 164, 173, 178, 180, 181, 193, 194, 196, 197, 200, 202, 208, 212, 218, 226, 229, 232, 233, 234
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OFFSET
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1,1
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COMMENTS
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Numbers k such that A342925(k) == 1 (mod 2).
Squares present in this sequence are terms of A347885 squared. (There are no even squares present, see A235991 for the explanation).
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LINKS
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FORMULA
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MATHEMATICA
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ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[234], OddQ[ad[DivisorSigma[1, #]]] &] (* Amiram Eldar, Sep 19 2021 *)
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CROSSREFS
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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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