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Search: id:A127644
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| A127644 |
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a(1)=3. a(n) is the smallest positive integer not occurring earlier in the sequence such that (sum{k=1 to n) a(k)) divides product{j=1 to n} a(j). |
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3
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| 3, 6, 9, 18, 12, 16, 8, 24, 32, 34, 30, 48, 15, 1, 14, 2, 17, 11, 20, 4, 26, 7, 21, 22, 5, 27, 10, 13, 25, 40, 19, 28, 33, 37, 23, 42, 38, 44, 35, 31, 41, 29, 46, 49, 39, 50, 36, 43, 47, 45, 51, 54, 55, 53, 52, 56, 57, 62, 61, 60, 64, 68, 67, 58, 63, 70, 69, 71, 65, 77, 66, 72
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Is this a permutation of the positive integers? According to Hans Havermann, this sequence matches sequence A127562 beginning with the 104th term of each. Unlike sequence A127562, the sum of the first n terms of this sequence divides the product of the first n terms for every positive integer n.
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MATHEMATICA
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f[l_List] := Block[{k = 1, s = Plus @@ l, p = Times @@ l}, While[MemberQ[l, k] || Mod[k*p, k + s] > 0, k++ ]; Append[l, k]]; Nest[f, {3}, 75] (*Chandler*)
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CROSSREFS
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Cf. A127562, A127645, A127646.
Sequence in context: A057855 A070120 A070126 this_sequence A047847 A007783 A050625
Adjacent sequences: A127641 A127642 A127643 this_sequence A127645 A127646 A127647
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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), Jan 22 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 22 2007
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