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A074873
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Friendly numbers (see A074902) such that sigma(n) is not friendly.
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0
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66, 210, 282, 364, 510, 642, 930, 966, 1080, 1092, 1146, 1624, 2130, 2226, 2346, 2586, 2676, 3560, 3810, 4278, 4872, 7965
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| I do not know how rigorously these numbers have been established. It is possible there are missing terms - see A074902. - N. J. A. Sloane (njas(AT)research.att.com), Sep 15, 2002
From Walter Nissen (http://upforthecount.com), May 28 2011: (Start)
Yes; in particular, if perchance 10 should turn out to have a friend, then 10 would be a(0). Also 30 and 40 might possibly be in this sequence.
Numbers without friends are called solitary.
(End)
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EXAMPLE
| 6 is friendly, but so is sigma(6)=12, so 6 is not in the sequence. 210 is friendly (with 17360 for example), but sigma(210)=576 is not friendly.
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CROSSREFS
| Sequence in context: A044779 A202647 A202640 * A205817 A046393 A117306
Adjacent sequences: A074870 A074871 A074872 * A074874 A074875 A074876
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KEYWORD
| nonn
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AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), Sep 12 2002
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