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A006580
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Sum lcm { k,n-k }, k = 1 . . n-1.
(Formerly M3336)
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2
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1, 4, 8, 20, 21, 56, 60, 96, 105, 220, 152, 364, 301, 360, 464, 816, 549, 1140, 760, 1036, 1221, 2024, 1196, 2200, 2041, 2484, 2184, 4060, 2205, 4960, 3664, 4224, 4641, 5180, 4008, 8436, 6517, 7072, 5980, 11480, 6321, 13244, 8888, 9540, 11661
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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REFERENCES
| Marc LeBrun (mlb(AT)well.com), personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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MATHEMATICA
| Table[ Sum[ LCM[ k, n-k ], {k, 1, n-1} ], {n, 2, 50} ]
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CROSSREFS
| Antidiagonal sums of array A003990.
Sequence in context: A083579 A065034 A178447 * A061814 A087254 A160726
Adjacent sequences: A006577 A006578 A006579 * A006581 A006582 A006583
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms and Mathematica Program Aug 15 1997 (Olivier Gerard).
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