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Search: id:A079851
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| A079851 |
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a(1) = 1, a(2) = 2 and a(n) is the smallest number such that all a(i)*a(j) are different. |
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4
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| 1, 2, 3, 4, 5, 7, 9, 11, 13, 16, 17, 19, 23, 25, 29, 30, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 81, 83, 84, 89, 97, 101, 103, 107, 109, 113, 121, 127, 128, 131, 137, 139, 149, 151, 154, 157, 163, 167, 169, 173, 179, 180, 181, 191, 193, 197, 199, 211, 223
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Taking a(n) as the smallest number such that a(i)+a(j) are all different gives the Fibonacci sequence (A000045) from third term onwards.
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EXAMPLE
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After 5, 7 is the next member and not 6 as 6*1 = 2*3.
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MATHEMATICA
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f[l_List] := Block[{k = 1, p = Times @@@ Subsets[l, {2}]}, While[Intersection[p, l*k] != {}, k++ ]; Append[l, k]]; Nest[f, {1, 2}, 62] (*Chandler*)
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CROSSREFS
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Cf. A000045, A079850, A079852, compare to A066724.
Sequence in context: A131180 A123193 A066724 this_sequence A089237 A009087 A026477
Adjacent sequences: A079848 A079849 A079850 this_sequence A079852 A079853 A079854
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 19 2003
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EXTENSIONS
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Corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 12 2007
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