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Search: id:A079854
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| A079854 |
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a(1) = 1, a(k) divides a(k+r) for all k and r and the ratios a(k+r)/a(k) are all different. |
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+0
1
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| 1, 1, 2, 6, 24, 120, 840, 6720, 60480, 604800, 6652800, 86486400, 1210809600, 18162144000, 308756448000, 4940103168000, 88921857024000, 1689515283456000, 35479820952576000, 780556060956672000, 17952789402003456000
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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a(7) != 120*1, 120*2, ..., 120*6 as the ratios 1,2,3,...,6 appeared as 1/1, 2/1, 6/2, 24/6, 120/24, 6/1. So a(7) = 7*120 = 840.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l], w, k = 1, r = l[[ -1]]/l}, w = Flatten[Table[Take[l, i - n]/l[[i]], {i, n}]]; While[Intersection[w, k*r] != {}, k++ ]; Append[l, k*l[[ -1]]]]; Nest[f, {1}, 21] (*Chandler*)
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CROSSREFS
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Cf. A000045, A079851, A079852, A036241.
Sequence in context: A129655 A114796 A114790 this_sequence A024923 A037992 A114779
Adjacent sequences: A079851 A079852 A079853 this_sequence A079855 A079856 A079857
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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 Fung Cheok Yin (cheokyin_restart(AT)yahoo.com.hk), Sep 30 2006
Edited and further extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 08 2007
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