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Search: id:A081887
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| A081887 |
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Numbers n such that LCM(1..n) equals denominator of sum of first n harmonic numbers. |
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+0
1
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| 1, 2, 4, 10, 12, 16, 28, 30, 52, 88, 96, 126, 130, 136, 138, 148, 150, 250, 256, 262, 268, 270, 292, 970, 976, 982, 990, 996, 1008, 1012, 1018, 1020, 1030, 1032, 1038, 1048, 1050, 1060, 1062, 1372, 1380, 1398, 1408, 1422, 1426, 1428, 1432, 1438
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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n+1 must be a prime, but converse is not true.
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EXAMPLE
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Sum of first 4 harmonic numbers is 77/12 and 12 is LCM[1,2,3,4]
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MATHEMATICA
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big=Table[LCM @@Range[n]/Denominator[ -n+(1+n) HarmonicNumber[n]], {n, 2048}]; Position[big, 1]//Flatten
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CROSSREFS
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Sequence in context: A138940 A129412 A113536 this_sequence A085344 A047463 A107059
Adjacent sequences: A081884 A081885 A081886 this_sequence A081888 A081889 A081890
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KEYWORD
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nonn
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AUTHOR
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Wouter Meeussen (wouter.meeussen(AT)pandora.be), Apr 13 2003; additional terms, Feb 21, 2004
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