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A125596
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a(1)=1. a(n) = sum{1<=k<n, GCD(k,n(n+1))=1} a(k).
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1
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1, 1, 1, 2, 1, 2, 3, 5, 4, 9, 5, 10, 12, 18, 21, 48, 22, 44, 48, 88, 84, 197, 92, 183, 260, 432, 441, 908, 183, 366, 1178, 1800, 1778, 3743, 1541, 3346, 5627, 8913, 7159, 16638, 7429, 14858, 24107, 38702, 38615, 88520, 40509, 79474, 88596, 167790, 169580
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| The positive integers < 8 and coprime to 8 and 9 are 1,5,7. So a(8) = a(1)+a(5)+a(7) = 1+1+3 = 5.
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MATHEMATICA
| f[l_List] := Block[{n = Length[l] + 1}, Append[l, Plus @@ l[[Select[Range[n], GCD[ #, n*(n + 1)] == 1 &]]]]]; Nest[f, {1}, 50] (*Chandler*)
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CROSSREFS
| Cf. A125597.
Sequence in context: A127462 A106436 A075758 * A204994 A132405 A057192
Adjacent sequences: A125593 A125594 A125595 * A125597 A125598 A125599
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Nov 26 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 26 2006
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