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Search: id:A122457
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| A122457 |
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a(1)=1, a(2)=1. a(n) = the sum of the two largest earlier terms which are both coprime to n. |
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+0
2
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| 1, 1, 2, 2, 4, 2, 6, 2, 6, 2, 12, 2, 18, 2, 6, 2, 30, 2, 48, 2, 6, 2, 78, 2, 126, 2, 6, 2, 204, 2, 330, 2, 6, 2, 282, 2, 612, 2, 6, 2, 942, 2, 1554, 2, 6, 2, 2496, 2, 3438, 2, 6, 2, 5934, 2, 9372, 2, 6, 2, 15306, 2, 24678, 2, 6, 2, 39984, 2, 64662, 2, 6, 2, 104646, 2, 169308, 2, 6
(list; graph; listen)
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OFFSET
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1,3
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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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a(1)=1, a(2)=1, a(3)=2, a(4)=2, a(5)=4, a(6)=2, a(8)=2 are the terms which are coprime to 9 and which occur among {a(1),a(2)...a(8)}. 2 and 4 are the two largest of these terms, so a(9) = 2 + 4 = 6.
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MATHEMATICA
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f[s_] := Append[s, Plus @@ Take[Sort[Select[s, GCD[ #, Length[s] + 1] == 1 &]], -2]]; Nest[f, {1, 1}, 74] (*Chandler*)
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CROSSREFS
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Cf. A122456.
Sequence in context: A082174 A074369 A073348 this_sequence A139770 A140635 A002322
Adjacent sequences: A122454 A122455 A122456 this_sequence A122458 A122459 A122460
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Sep 07 2006
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EXTENSIONS
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Corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and Robert G. Wilson v, Sep 11 2006
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