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Search: id:A060695
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| 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 30, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 60, 31, 32, 33, 34, 70, 36, 37, 38, 39, 40, 41, 42, 43, 44, 90, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 126, 64, 65, 66, 67, 68, 69, 140, 71
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OFFSET
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1,2
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FORMULA
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Table[GCD[2*w, Apply[LCM, dd[2w]]], {w, 1, 512}], where dd[x] is the first difference set of divisors of x.
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EXAMPLE
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a(n)=a(2k) is either n=2k or n/2=k. a(n)=n/2 seems regular, a(n)=n seems "anomalous". n=30:D={1, 2, 3, 5, 6, 10, 15, 30}, dD={1, 1, 2, 1, 4, 5, 15}={1, 2, 4, 5, 15}, LCM[dD]=60, GCD[n, LCM[dD[n]]]=GCD[30, 60]=30=n n=36:D={1, 2, 3, 4, 6, 9, 12, 18, 36}, dD={1, 1, 1, 2, 3, 3, 6, 18}={1, 2, 3, 6, 18}, LCM[dD]=18, GCD[n, LCM[dD[n]]]=GCD[36, 18]=18=n/2
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CROSSREFS
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Cf. A060680-A060685, A060741, A060742, A060763-A060766, A000005.
Sequence in context: A023795 A032949 A094275 this_sequence A055646 A161952 A043319
Adjacent sequences: A060692 A060693 A060694 this_sequence A060696 A060697 A060698
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Apr 25 2001
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