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Search: id:A125168
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| A125168 |
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a(n)=gcd(n,b(n)) where b(n)=the number of proper divisors of n. |
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+0
1
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| 1, 1, 1, 2, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 5, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 4, 1, 1, 3, 1, 1, 7, 1, 1, 5, 1, 1, 3, 1, 5, 3, 1, 1, 1, 1, 7, 3, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 7, 1, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 7
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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First occurrence of k: 1, 4, 6, 16, 20, 3240000, 42, 256, 162, 18662400, 132, 5308416, 832, 784, 120, 65536, 612, 2985984, 912, 1600, 9240, 98010000, 1380, 1296, 100800, ..., (10^7). - Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 23 2007
Do all values appear? - Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 23 2007
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EXAMPLE
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a(6)=3 because 6 has 3 proper divisors {1,2,3} and the gcd(6,3) is 3.
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MATHEMATICA
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f[n_] := GCD[n, DivisorSigma[0, n] - 1]; Array[f, 105] (* Robert G. Wilson v *).
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CROSSREFS
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Cf. A032741, A009191.
Adjacent sequences: A125165 A125166 A125167 this_sequence A125169 A125170 A125171
Sequence in context: A072127 A119805 A111957 this_sequence A051794 A110969 A006083
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KEYWORD
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easy,nonn
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AUTHOR
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Mitch Cervinka (puritan(AT)toast.net), Jan 12 2007
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 23 2007
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