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Search: id:A124693
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| A124693 |
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a(1)=1. a(n+1) = sum a(k), where the sum is over all positive integers k, k <= n, where each positive integer <= k and coprime to k is also coprime to n. |
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+0
1
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| 1, 1, 2, 4, 6, 14, 16, 44, 64, 82, 88, 322, 338, 982, 1002, 1006, 2456, 6428, 6766, 19622, 19710, 19728, 19874, 98556, 105322, 126042, 126510, 252610, 253612, 1061208, 1061210, 3183626, 4770276, 4770358, 4772814, 4772828, 5939358, 31392886
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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The positive integers k, where k <= 6, and where each positive integer <= k and coprime to k is also coprime to 6, are 1,2,6. So a(7) = a(1)+a(2)+a(6) = 1+1+14 = 16.
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MATHEMATICA
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f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &]; h[l_List] := Append[l, Plus @@ l[[g[Length[l]]]]]Nest[h, {1}, 38] (*Chandler*)
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CROSSREFS
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Cf. A126260.
Sequence in context: A105543 A027712 A138307 this_sequence A095698 A064409 A032353
Adjacent sequences: A124690 A124691 A124692 this_sequence A124694 A124695 A124696
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Dec 25 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 26 2006
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