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Search: id:A143772
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| A143772 |
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If m is the nth composite, then a(n) = GCD(k +m/k), where k is over all divisors of m. |
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+0
2
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| 1, 1, 3, 2, 1, 1, 3, 8, 1, 1, 3, 2, 1, 1, 2, 3, 4, 1, 1, 3, 2, 1, 12, 1, 3, 8, 1, 1, 3, 2, 1, 1, 2, 3, 4, 1, 1, 8, 3, 2, 1, 1, 3, 8, 1, 6, 1, 3, 2, 1, 1, 3, 4, 1, 6, 1, 3, 2, 1, 1, 2, 3, 8, 1, 1, 4, 3, 2, 1, 24, 1, 3, 4, 1, 1, 3, 2, 1, 1, 3, 8, 1, 1, 4, 3, 2, 1, 24, 1, 2, 3, 4, 1, 6, 1, 3, 2, 1, 1, 2, 3, 8, 1, 1, 3
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Conjecture: All even numbers are members and the only odd numbers which are members are 1 & 3. [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 08 2008]
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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For n=11, 20 is the 11th composite. So we have: a(11) = GCD(1+20,2+10,4+5,5+4,10+2,20+1) = 3.
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MATHEMATICA
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Composite[n_Integer] := FixedPoint[n + PrimePi@# + 1 &, n + PrimePi@n + 1]; f[n_] := Block[{m = Composite@n}, Last@ FoldList[ GCD, m!, # + m/# & /@ Divisors@m]]; Array[f, 105] [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 08 2008]
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CROSSREFS
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Cf. A143771.
Sequence in context: A152176 A152175 A134520 this_sequence A053989 A097794 A137683
Adjacent sequences: A143769 A143770 A143771 this_sequence A143773 A143774 A143775
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Aug 31 2008
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 08 2008
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