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Search: id:A126870
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| A126870 |
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a(1)=1. a(n) = number of earlier terms of the sequence which are coprime to the sum of distinct prime divisors of n. |
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+0
1
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| 1, 1, 2, 2, 4, 5, 6, 3, 6, 9, 10, 9, 12, 7, 7, 8, 16, 15, 18, 17, 8, 21, 22, 20, 20, 12, 16, 17, 28, 10, 30, 12, 9, 33, 7, 28, 36, 17, 16, 33, 40, 9, 42, 43, 19, 37, 46, 39, 41, 42, 21, 24, 52, 45, 25, 32, 24, 57, 58, 23, 60, 34, 24, 28, 15, 29, 66, 65, 29, 27, 70, 57, 72, 39, 35
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OFFSET
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1,3
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EXAMPLE
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The sum of the distinct prime divisors of 12 is 2+3 = 5. So a(12) is the number of terms from among (a(1),a(2),...a(11)) which are coprime to 5. There are 9 such terms, so a(12) = 9.
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MATHEMATICA
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g[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[GCD[l, f[n]], 1]]]; Nest[g, {1}, 75] (*Chandler*)
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CROSSREFS
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Cf. A008472.
Sequence in context: A049269 A085085 A121600 this_sequence A137413 A010848 A133937
Adjacent sequences: A126867 A126868 A126869 this_sequence A126871 A126872 A126873
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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), Mar 16 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 26 2007
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